HomeArchiveWellington Statistics Group

Wellington Statistics Group: Archive of Presentations

Index
2015
4 November 2015, John Maindonald
2014
9 May 2014, James Curran
2013
15 August 2013, Peter Ellis and Ian Westbrooke
2012
6 March 2012, Peter Jupp
2011
2 February 2011, John Maindonald
2010
2 July 2010, Ingram Olkin
26 May 2010, Shirley Pledger and Richard Arnold
9 February 2010, John Maindonald
2009
8 September 2009, Vijay Nair
2 April 2009, Ross Ihaka
2 February 2009, Brian Easton and Ryan You
2008
20 October 2008, Jim Ridgway
3 June 2008, Pra Murthy
23 April 2008, Nicholas Horton
3 April 2008, Ray Chambers
18 March 2008, Jiancang Zhuang
4 March 2008, Martin Bland
7 February 2008, J.P. Lewis
2007
4 December 2007, I-Ming Liu
20 November 2007, Mike Camden and Paul Cowie
24 October 2007, Jim Renwick
18 September 2007, Peter Thomson
6 August 2007, Nick Longford
9 May 2007, Shirley Pledger
18 April 2007 (6pm), Stephen E. Fienberg
18 April 2007 (Noon), Stephen E. Fienberg
16 April 2007, Stephen E. Fienberg
22 March 2007, Richard Arnold
2006
28 November 2006, Nanny Wermuth
22 November 2006, Estate Khmaladze
1 November 2006, Len Cook
12 October 2006, Dimitar Christozov and Stefanka Chukova
25 July 2006, Edith Hodgen, Rachel Dingle and Hilary Ferral
20 June 2006, Ian Westbrooke
16 March 2006, Geoff Chambers
2005
13 December 2005, Rod Lea
8 November 2005, Tony Vignaux
14 September 2005, Paul Jose
2 August 2005, Phil Lester
19 May 2005, Statistical Education
13 April 2005, Mark Weatherall
24 February 2005, Tim Ball
2004
7 December 2004, Estate Khmaladze
18 November 2004, Robin Willink
30 September 2004, Robert Davies
27 May 2004, Jeff Robinson
29 April 2004, James Liu
25 March 2004, Shirley Pledger
11 February 2004, Brian Easton
2003
26 November 2003, Stefanka Chukova and Yu Hayakawa
28 October 2003, Nick Longford
14 August 2003, Caroline Roughneen
9 July 2003, Mark Weatherall
11 June 2003, Leigh Bull
1 May 2003, Chris Francis
27 March 2003, Srinivas Chakravarthy
2002
17 October 2002, Frances Krsinich and Mike Camden
27 August 2002, Paul Dyer
24 July 2002, Jean Thompson
21 February 2002, Richard Arnold
2001
6 December 2001, Brian Bull
16 October 2001, Dean Hyslop and Dave Mare
8 August 2001, Brian Pink





4 November 2015, John Maindonald

Speaker: John Maindonald, Australian National University

(Joint seminar with the Faculty of Science, VUW)

Title: Reproducibility in Science – Rethink, or Crisis?

Time: 5:30 – 6.30pm, Wednesday 4 November

Place: MacLaurin Building Lecture Theatre 102, VUW, Kelburn Parade (Gate 4)

Abstract:
Reproducibility issues in scientific studies have received a lot of attention in the past several years, particularly those related to animal and drug laboratory studies, and experimentation in psychology and neuropsychology. A recent attempt at reproducing 67 ‘seminal’ drug studies was successful in just 14 instances, for example.
John Maindonald will discuss what this means for science and he will comment on pertinent statistical issues. He will note initiatives that are designed to address the problem, and will highlight the misuse and misunderstanding of P-values in ways that compromise the scientific process.
There are radical implications for the management of the research process, study design and analysis, the reporting and publication process and for funding. Moves towards larger cooperative studies and greater transparency in reporting the total research process would help greatly.
The slides (pdf) for John’s presentation are available here.

About the Speaker:
John Maindonald has held many academic roles, including at the Australian National University Centre for Bioinformation Science. He is the author of a book on statistical computation, and the senior author of “Data Analysis and Graphics Using R”. Now in semi-retirement, he does occasional consulting, holds workshops on the R system and continues to write. John has recently moved back to NZ and now lives in Wellington.

 


9 May 2014, James Curran

Speaker: James Curran, University of Auckland

Title: Adventures in Forensic Statistics

Time: 4:10 – 5.00pm, Friday 9 May (light refreshments from 5:00pm, after the talk)

Place: Room LT118, Laby building, Kelburn campus (Gate 6 or 7), VUW

Abstract:
Incredible developments in science and technology have given forensic scientists a powerful arsenal of tools for the detection, recovery, and quantification of evidence. Modern instrumentation can produce a DNA profile from a single human cell under ideal conditions, and from 5-6 cells under casework conditions. Similarly, current generation mass spectrometry equipment can detect differences in compounds in the parts per billion range. Quantifying evidence, however, is only one part of the legal process. The court wants to know “Does this piece of evidence make the defendant more likely to be guilty or innocent?” In order to answer this question we need statistics. All measurements have inherent variability, and where there is variability there is uncertainty and there are statisticians. In this talk I will explain the role of a statistician in forensic evidence interpretation and discuss some of the research questions that my collaborators and I have addressed over the last 20 years.

About the Speaker:
James Curran is a Professor of Statistics at the University of Auckland. His main research area is statistical problems in forensic science. He also has strong interests in statistical computing, and in automation projects. James is the current President of the NZ Statistical Association.

 


15 August 2013, Peter Ellis and Ian Westbrooke

Speakers: Peter Ellis (MBIE) and Ian Westbrooke (DOC)

Title: Calling R Users in Wellington: R code/tips and a WRUG to take home

Time: 6:00pm, Thursday 15 August (light refreshments from 5:30pm)

Place: Room GB LT2, VUW Law School, Government Buildings, 55 Lambton Quay (in the concrete building behind the main wooden building, when viewed from Lambton Quay)

Abstract:
This meeting follows on from the wide interest in the Official Statistics Seminar on June 13 in Wellington, “Statistical Analysis in The Government Sector Using R Language: Experiences from MBIE and DOC”. The meeting will open with brief practical presentations on techniques you can take away and use, on three applied topics that were mentioned in passing in the previous seminar. Each of these topics will involve 8-10 minutes plus question/comment time:

Workflow and example code for creating animations out of statistical graphics;
Using R Commander as a bridge for new users to write code, (including ggplot2);
Defining statistical transformations for ggplot2 to perform rolling average or seasonal adjustment on the fly.

Following that we will invite discussion about forming a Wellington R User Group (WRUG), and ask for volunteers to be involved in organizing any further activities.

About the Speakers:
Peter Ellis is Manager, Sector Performance, in the Ministry of Business, Innovation and Employment. His past work experience includes managing the Australian aid programme to East Timor from the embassy in Dili, directing the AusAID evaluation team in Canberra, and performance information improvement at New Zealand MFAT. He has published on Australian voting behaviour, ethics for aid organisations, and incentive-based aid. He has a Masters in Applied Statistics from ANU.

Ian Westbrooke is Principal Science Advisor, Statistician, at the Department of Conservation, based in Christchurch. Ian has presented on his experiences on teaching statistics at international conferences and in a forthcoming book, and has taught courses on statistical analysis using R at DOC and MBIE, as well as at universities and workshops in New Zealand, Australia and Fiji.

 


6 March 2012, Peter Jupp

Speaker: Peter Jupp, University of St Andrews

Title: Statistics and Geometry: surprisingly interesting?

Time: 6:00pm, Tuesday 6 March (light refreshments from 5:30pm)

Place: Room GB LT4, VUW Law School, Government Buildings, 55 Lambton Quay (1st floor, north wing at back)

Abstract:
There are surprising interactions between geometry and statistics. Some of these form the area of directional statistics, in which the observations are not counts, numbers or vectors but directions (or more complicated geometrical objects). This talk aims to use examples from various fields of application to give the flavour of the unexpected pleasures of directional statistics.

About the Speaker:
Peter Jupp is the 2012 Shayle Searle Visiting Fellow in Statistics at Victoria University and a Professor in the School of Mathematics and Statistics at the University of St Andrews, Scotland.

 


2 February 2011, John Maindonald

Speaker: John Maindonald, Australian National University

(Joint seminar with the School of Mathematics, Statistics and Operations Research, VUW)

Title: Statistical Training or Retraining for the Age of Data Mining, Machine Learning, and Analytics

Time: 2:00 – 3.00pm, Wednesday 2 February

Place: Cotton building, room CO 350 (third floor), VUW Science Faculty, Kelburn Parade (Gate 6)

Abstract:
Data Mining, Analytics and (to a lesser extent) Machine Learning are buzzwords for enterprises that are hard to distinguish from statistics. Statisticians may be rightly wary of some of the styles of data analysis that are promoted, in particular under the name “data mining”. More positively, ideas and insights associated with these buzzwords provide useful entry points for debating the style of teaching to which it may now in 2011 be useful to expose intending data analysts and statistical modelers.
Recent experience in teaching a course in ‘Statistical Learning and Data Mining’ as part of the ACSPRI (Australian Consortium for Social and Political Research Inc) summer series highlighted such issues. (See http://www.acspri.org.au/courses)

 


2 July 2010, Ingram Olkin

Speaker: Ingram Olkin, Stanford University

Title: Meta-Analysis: History and Statistical Issues for Combining the Results of Independent Studies

Time: 6:00pm, Friday 2 July (light refreshments from 5:30pm)

Place: Room RH LT3, Rutherford House, Lambton Quay

Abstract:
Meta-analysis enables researchers to synthesize the results of independent studies so that the combined weight of evidence can be considered and applied. Increasingly meta-analysis is being used in medicine and other health sciences, in the behavioral and educational fields to augment traditional methods of narrative research by systematically aggregating and quantifying research literature.
Meta-analysis requires several steps prior to statistical analysis: formulation of the problem, literature search, coding and evaluation of the literature, after which one can address the statistical issues.
We here review some of the history of meta-analysis and discuss some of the problematic issues such as various forms of bias that may exist. The statistical techniques that have been used are nonparametric methods, combining proportions, the use of different metrics, and combining effect sizes from continuous data.

About the Speaker:
Professor Ingram Olkin (Stanford University) is the NZSA Visiting Lecturer for 2010. His visit to New Zealand is sponsored by Statistics New Zealand and is associated with the International Conference on Statistical Methodologies and Related Topics, in conjunction with the NZSA 2010 Conference, 29 June – 1 July 2010, Massey University, Palmerston North.
Dr Olkin is an icon in the world statistical community, having been active for over 60 years. He is a member of many professional societies, has received many honours and awards, has held and holds many editorial positions, and has delivered numerous invited addresses all over the world. Ingram has coauthored 7 books, edited 10 books, and contributed 220 journal papers. His joint paper with Albert Marshall “A multivariate exponential distribution” was cited in over 600 articles.
Dr Olkin’s work is aimed at ensuring that educators select the proper statistical tools for measuring the outcomes of their programs and methods, and that their interpretation of the results is similarly rigorous. His research includes the development of powerful new statistical methods for combining results from independent studies that have analysed the same topic. Meta-analysis is assisting researchers to reconsider long-standing educational problems with a fresh critical eye.
Dr Olkin is a Guggenheim, Fulbright, and Lady Davis Fellow, with an honorary doctorate from De Montfort University. He received his BS in mathematics at the City College of New York, his MA from Columbia University, and his PhD from the University of North Carolina. Dr Olkin’s research interests include analysis of social and behavioural models; multivariate statistical analysis; correlational and regression models in educational processes; and meta-analysis.

 


26 May 2010, Shirley Pledger and Richard Arnold

Speakers: Shirley Pledger and Richard Arnold, Victoria University

Title: Clustering and Pattern Detection in Ecological Models Using Mixtures

Time: 6:00pm, Wednesday 26 May (light refreshments from 5:30pm)

Place: Room RH LT2, Rutherford House, Lambton Quay

Abstract:
Incidence matrices record the presence or absence of species in particular habitats or locations, while abundance matrices record the count of each species. Such matrices can be used to identify species which associate, and the habitats in which they do so. This can be achieved by clustering the rows or the columns of an incidence or abundance matrix, or clustering both rows and columns simultaneously.
Finite mixture models – where species and habitats are separately and probabilistically classified into groups – provide a tractable means of carrying out this clustering, and yield results which are readily interpretable in their ecological context. We will present a likelihood-based approach to the two-way clustering using finite mixtures.
Further developments provide likelihood-based analogues of a range of multivariate techniques, including correspondence analysis and multidimensional scaling, which traditionally use matrix decompositions. Generally the mixture modelling gives clustering and ordination results similar to those from the standard methods, but with extra information available from the likelihoods for pattern description and statistical analysis.

 


9 February 2010, John Maindonald

Speaker: John Maindonald, Australian National University

Title: Mining a Cricketer Data Archive

Time: 6:00pm, Tuesday 9 February (light refreshments from 5:30pm)

Place: Room LT4, VUW Law School, Old Government Buildings, Lambton Quay (First floor, north wing at back)

Abstract:
The data, compiled by psychologist John Aggleton from information in the “Who’s Who of Cricketers”, has details on the birth year and bowling hand of British first class cricketers who were born in one of the years 1840–1960. For those who died in 1990 or earlier, age at death is recorded. Also noted are instances of death by accident, or in war.
Martin Bland and Douglas Altman used the data to investigate whether left-handed cricketers die young. There is more that can be gleaned from these data. They provide a commentary on the dislocation that World War 1 caused to British society.
This has been an exercise in data mining, with a relatively automated use of what are now standard statistical learning approaches, here used to criticise and supplement more classical approaches. As happens here, data frequently have a value that extends beyond the use for which they were initially collected.

 


8 September 2009, Vijay Nair

Speaker: Vijay Nair, University of Michigan

Title: Statistical Inverse Problems in Network Tomography and Monitoring Quality of Service Characteristics in Networks

Time: 6:00pm, Tuesday 8 September (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
The term network tomography refers to two classes of large-scale inverse problems that arise in the modeling and analysis of computer and communications networks. The first deals with passive tomography where aggregate data are collected at the individual router/node level and the goal is to recover path-level information. The main problem of interest here is the estimation of the origin-destination traffic matrix. The second, sometimes referred to as active tomography, deals with reconstructing link-level information from end-to-end path-level measurements obtained by actively probing the network. The primary application in this case is estimation of quality-of-service parameters such as loss rates and delay distributions. Internet service providers use this to characterize network performance and to monitor service quality. We will review both classes of inverse problems with a focus on active tomography. We will provide a review of recent developments, including the design of probing experiments, inference for loss rates and delay distributions, and applications to network monitoring. This is joint work with George Michailidis, Earl Lawrence, Bowei Xi, and Xiaodong Yang.

About the Speaker:
Vijay Nair is the Donald A. Darling Professor and Chair of Statistics, and the Professor of Industrial and Operations Engineering at the University of Michigan. He is also a current Vice President of the International Statistical Institute. Prof Nair is the 2009 Shayle Searle Visiting Fellow in Statistics at Victoria University.

 


2 April 2009, Ross Ihaka

Speaker: Ross Ihaka, The University of Auckland and the R Foundation

Title: R : Past and Future History

Time: 6:00pm, Thursday 2 April (light refreshments from 5:30pm)

Place: Room LT4, VUW Law School, Old Government Buildings, Lambton Quay (1st floor, north wing at back)

Abstract:
R is a free software environment for statistical data analysis. It began life as a purely academic experiment, but has developed into one of the more widely-used statistical software environments.
This talk will describe how R came into being and developed into its current state. It will describe the current state of R development and also cover more recent work which seeks to deliver even better computing environments.

 


2 February 2009, Brian Easton and Ryan You

Speakers: Brian Easton and Ryan You

Title: Measuring Gambling Experiences of New Zealanders

Time: 6:00pm, Monday 2 February (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
In 2008, the Centre for Social and Health Outcomes Research and Evaluation (SHORE) at Massey University published a study based on the gambling experiences of 7000 New Zealanders. Brian Easton and Ryan You will report on the statistical work they did to assess the extent to which gambling affects individual’s welfare.

 


20 October 2008, Jim Ridgway

Speaker: Jim Ridgway, School of Education, University of Durham UK

Title: The OECD Global Project – Measuring the Progress of Societies, Thoughts and Actions

Time: 6:00pm, Monday 20 October (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
The OECD has launched the Global Project on Measuring the Progress of Societies (GP) to encourage the use of new indicator systems in order to inform and promote evidence-based decision-making within and across the public and private sectors. Put baldly, the GP aims to invigorate democracies by getting citizens involved with the creation of measures of societal progress, and by holding governments to account on a raft of measures, “beyond GDP”. There is an underlying belief that an emphasis on economic indicators alone is a recipe for global disaster. Statistics and statisticians have a central role to play, and key concepts in statistics need to be absorbed into the “common sense” of engaged citizens.

There are a number of key activities, including:

  • Eliciting what communities think “progress” means in the 21st century;
  • Advocating appropriate investment in building statistical capacity;
  • Developing and sharing good practices on the measurement of societal progress (with an emphasis on using sound and reliable methodologies);
  • Producing a broader, shared, public understanding of changing global conditions, while highlighting areas of the most dramatic changes and of inadequate knowledge; and
  • Stimulating international debate, based on solid statistical data and indicators, on both global issues of societal progress and comparisons of such progress.

This paper will provide experiences of some of the activities in the first OECD training session for statisticians, held in Siena in September 2008, and will show some visualization tools designed to facilitate the transition from data to knowledge.

The whole enterprise is conceptually and technically challenging. I hope we can explore these challenges in the discussion.

 


3 June 2008, Pra Murthy

Speaker: Pra Murthy, University of Queensland

Title: Warranty: An Introduction

Time: 6:00pm, Tuesday 3 June (light refreshments from 5:30pm)

Place: Room LT4, VUW Law School, Old Government Buildings, Lambton Quay (1st floor, north wing at back)

Abstract:
Most products (consumer, industrial and commercial) are sold with warranty. A warranty is a contractual agreement which requires the manufacturer to repair, replace or provide some compensation for failures occurring within the warranty period. There are various aspects to warranty and they have been studied from different perspectives. The seminar will give an overview of this.

 


23 April 2008, Nicholas Horton

Speaker: Nicholas Horton, Smith College, Northampton MA

Title: What your physician should know about statistics but perhaps doesn’t: The implications of the increasing sophistication of statistical methods in medical research

Time: 6:00pm, Wednesday 23 April (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
A recent survey of original articles published in The New England Journal of Medicine revealed increasing use of statistical methods over time, compared with surveys conducted in 1979 and 1989 by Emerson and Colditz. Of 311 articles published in 2004–2005, a substantial fraction of articles utilized relatively sophisticated statistical methodologies such as survival analysis (61%), multiple regression (51%) or power calculations (39%). Only 13% of articles used just simple descriptive statistics (e.g. percentages, means, confidence intervals). Knowledge of material typically included in an introductory statistics course increased this percentage to only 21%. The statistical training required prior to entry into as well as that provided during medical school is quite minimal, and this increasing sophistication complicates the interpretation and dissemination of new results, particularly for clinicians who have not received additional training in the conduct of research. We discuss the implications of this increased use of sophisticated statistical methods for medical and statistical education.

 


3 April 2008, Ray Chambers

Speaker: Ray Chambers, University of Wollongong, and NZSA Visiting Lecturer for 2008

Title: Measurement Error in Auxiliary Information

Time: 6:00pm, Thursday 3 April (light refreshments from 5:30pm)

Place: Room LT4, VUW Law School, Old Government Buildings, Lambton Quay (1st floor, north wing at back)

Abstract:
Auxiliary information is information about the target population of a sample survey over and above that contained in the actual data obtained from the sampled population units. The availability of this type of information represents a key distinction between sample survey inference and more mainstream inference scenarios. In particular, modern methods of sampling inference (both model-assisted as well as model-based) depend on the availability of auxiliary information to improve efficiency in survey estimation. However, such information is not always of high quality, and typically contains errors. In this talk I focus on some survey-based situations where auxiliary information is crucial, but where this information is not precise. Estimation methods that allow for this imprecision will be described. In doing so I will not only address the types of inference of concern to sampling statisticians (e.g. prediction of population quantities), but also inference for parameters of statistical models for surveyed populations.

About the Speaker:
Ray Chambers is Professor of Statistical Methodology at the University of Wollongong. He has extensive research interests in the design and analysis of sample surveys, official statistics methodology, robust methods for statistical inference and analysis of data with group structure. He is also the NZSA Visiting Lecturer for 2008.

 


18 March 2008, Jiancang Zhuang

Speaker: Jiancang Zhuang, Institute of Statistical Mathematics, Tokyo

Title: Visualizing patterns in earthquake clusters by using a point process model

Time: 6:00pm, Tuesday 18 March (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
Point processes have been widely used in modelling seismicity, and other natural and social phenomena. Among them, the epidemic-type aftershock sequence (ETAS) model is a space-time continuous-type point process for describing the clustering behaviour of earthquake occurrences. This talk gives a real example using this model to analyze characteristics and test hypotheses associated with earthquake clustering. Such questions include the relationship between the size of ancestor events to the number of triggered events (offspring), the size of the region, etc. A form of model residual analysis will also be described and shown how it can be used as a powerful tool in model improvement.

 


4 March 2008, Martin Bland

Speaker: Martin Bland, Professor of Health Statistics, University of York, England

Title: Risedronate, the BBC, and me

Time: 6:00pm, Tuesday 4 March (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
Risedronate is a drug used to reduce fractures in women with osteoporosis. The story of the Sheffield Risedronate trial was national news. One of the clinical researchers, Aubrey Blumsohn, dissociated himself from the trial because he was refused access to the data he had helped to collect. He did not believe the analysis provided by the pharmaceutical company statistician. Then some of the data were obtained. I shall describe how I came to analyse the data on behalf of the BBC, what I found, and what happened next.

About the Speaker:
Prof Bland coauthored a paper with Doug Altman in 1986 that was published in the Lancet, and titled “Statistical Methods for Assessing Agreement”. By 1992 it became a citation classic, and by April 2010 it had been cited over 16,800 times. A copy of the paper (and much other material) can be found on his web page: http://www-users.york.ac.uk/~mb55/.

 


7 February 2008, J.P. Lewis

Speaker: J.P. Lewis, Weta Digital (contractor)

Title: Statistical Applications in Computer Graphics

Time: 6:00pm, Thursday 7 February (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
Computer graphics modeling and animation have traditionally been approached as a craft, using models that are manually constructed and animated. With plentiful computer storage and techniques such as non-parametric regression it is increasingly possible to build models directly from data, as well as to characterize the ways that these models change. This talk will describe film and gaming applications such as character skinning, eye movement synthesis, and automatic caricature, and present research on identifying and characterizing structure in multidimensional data. The discussion will reference PCA, kernel density, robust norms, MDL, and graph cuts.

 


4 December 2007, I-Ming Liu

Speaker: Ivy (I-Ming) Liu, Victoria University of Wellington

Title: The analysis of ordered response data

Time: 6:00pm, Tuesday 4 December (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
This talk has two parts. First, I will review methodologies used for analysing ordered categorical (ordinal) response variables by introducing models for data with a single ordinal response variable. The second part is based on the talk given at the International Statistical Institute Conference in August 2007. It provides graphical methods for checking the adequacy of the proportional odds model, which is currently the most popular model for ordinal responses. The methods using the cumulative sums of residuals focus on evaluating model misspecification for specific covariates.

 


20 November 2007, Mike Camden and Paul Cowie

Speakers: Mike Camden and Paul Cowie, Statistics New Zealand

Title: Confidentiality and Census Counts: the best of both worlds

Time: 6:00pm, Tuesday 20 November (light refreshments from 5:30pm)

Place: Room LT2, VUW Law School, Old Government Buildings, Lambton Quay (note that GB LT2 is in the lecture block behind the old wooden building)

Abstract:
Tables of counts from our Census of Population and Dwellings are valued highly by users, especially users from local government. The Census also appear to be valued and strongly supported by the 4,249,737 respondents, who form about 98% of the population. The two worlds are those of users and respondents, and they are interested in data utility and safety respectively. Users request detailed tables that are often very sparse. Statistics New Zealand’s past protections against sparseness include random rounding to base 3 and a mean cell size rule. We decided, for our 2006 Census, to further enhance data utility and protect safety by setting a threshold for sparse tables: counts above this are released and counts at this value or below are suppressed.
The confidentiality rules are applied to each geographical area separately, and our current geographical areas vary widely in population. This variation is a source of sparseness, but we turn this liability into an asset. For each of our widely varying Area Units, we calculate measures for utility and safety, and get some expected and unexpected messages from the data, via some data visualisation. We use this data to evaluate the threshold approach, and also to help in setting the size for a possible new set of geographical areas for NZ, designed for output. We hope to use these results to heighten utility and safety for NZ’s Census 2011.
Presenters: Paul and Mike both work in the Statistical Methods Division of Statistics NZ, and both spend much of their time aiming to ensure that NZ has the best confidentiality systems available. Paul is a graduate from the University of Auckland, in statistics and commerce, and Mike has done time at Auckland, Waikato and VUW. The talk is an expanded version of Statistics NZ’s contribution to the Joint UNECE/Eurostat Work Session on Statistical Data Confidentiality in December.

 


24 October 2007, Jim Renwick

Speaker: Jim Renwick, NIWA, Wellington

Title: Recent climate change assessment: physical science and statistical interpretation

Time: 6:00pm, Wednesday 24 October (light refreshments from 5:30pm)

Place: Room HMLT001, Hugh MacKenzie Building, Kelburn Parade (note the change of location)

Abstract:
The Intergovernmental Panel on Climate Change (IPCC) recently released its fourth Assessment Report (AR4), covering past observations of climate changes and projections of likely future global changes. This presentation will summarise the role of the IPCC, and outline some of the key messages from the AR4 in terms of both the past and the future. Beyond the physics of climate and climate change, the talk will cover some aspects of climate change monitoring and prediction, including the estimation of probability densities for climate parameters in the future.
Speaker: Dr James Renwick leads a research programme on climate variability and change at NIWA in Wellington. His interests include Southern Hemisphere climate variability and impacts of climate on the New Zealand environment. He has worked in the area of climate and atmospheric dynamics and statistics since the late 1970s, starting as a weather forecaster at the Meteorological Service and completing a MSc through ISOR at Victoria University in the late 1980s. He was a lead author on Working Group I of the IPCC 4th Assessment Report, dealing with observed changes to the large-scale circulation of the atmosphere.

 


18 September 2007, Peter Thomson

Speaker: Peter Thomson, Statistics Research Associates Ltd

Title: Hidden Markov models: some examples of their application and reflections on their use

Time: 6:00pm, Tuesday 18 September (light refreshments from 5:30pm)

Place: Room LT3, VUW Law School, Old Government Buildings, Lambton Quay (Ground floor, north wing at back)

Abstract:
Hidden Markov models were first introduced in the statistical literature by Baum and his colleagues in the late 1960s and have since become widely used in many disciplines including meteorology, economics, finance and speech recognition, to name but a few. In effect, a hidden Markov model (HMM) blocks time series data into consecutive periods of time (regimes) within which the observations follow a simple regime-dependent time series model. Switching to and from regimes is governed by an unobserved (hidden or latent) Markov chain or variant thereof. In this way the time evolution of regimes is directly modelled as is the evolution of the observations within regimes. This conceptually simple and open structure allows direct modelling of time and spatial scales that may be present in the data, as well as opportunities for enhanced interpretation and more physically based models.
The advantages and limitations of using hidden Markov models in practice will be discussed with reference to the particular HMM applications in which we have been involved. These will mainly focus on modelling rainfall (daily and high frequency) and GDP growth rates (quarterly), with other applications in finance and river-flow modelling (actual and potential) mentioned in passing. The focus will be on practical rather than technical issues and, in particular, the need to explore and exploit the structure of HMMs.

 


6 August 2007, Nick Longford

Speaker: Nick Longford, SNTL, Reading, England

Title: Allocation of limited resources and related problems in small-area statistics

Time: 6:00pm, Monday 6 August (light refreshments from 5:30pm)

Place: Room LT4, VUW Law School, Old Government Buildings, Lambton Quay (1st floor, north wing at back)

Abstract:
Small-area statistics is the generic term used for estimation of one or a set of quantities associated with each district of a country. Development of methods for small-area estimation has been motivated mainly by the increased demand for more and more detailed information about the social, economic, health-related and other processes in a country that are in the remit of its government. The key principle in small-area estimation is borrowing strength, or exploiting similarity of the districts. The overall research strategy may be summarised as follows: first we estimate as efficiently as possible the quantities that our clients would ideally like to have, and then we let them handle the estimates as if they were the underlying (population) quantities, after instructing them about standard errors or confidence intervals.
The talk will discuss an attempt to distribute a fixed budget to the districts of a country for combating a specific problem, such as high unemployment. The distribution is to be based on district-level estimates of the quantity of interest (unemployment rate). It is easy to show, by simulations, that efficient estimation is not conducive to effective distribution of the budget. Some solutions better than efficient estimation are proposed, but they do not have a straightforward derivation. The problem is connected to the use of estimates in general, and the conclusion implies that the separation of the activities of estimation and decision making, which promotes integrity of one kind, results in suboptimal decisions.
The talk will be of interest to lecturers of elementary statistics, as the ANOVA, hypothesis testing, and a few similar rituals will be exposed as way past their due dates, not only for the practice, but even for the curriculum.

 


9 May 2007, Shirley Pledger

Speaker: Shirley Pledger, School of Mathematics, Statistics and Computer Science, Victoria University of Wellington

Title: Something for Nothing: Estimating age-related survival rates from capture-recapture data when age is unknown

Time: 6:00pm, Wednesday 9 May 2007 (light refreshments from 5:30pm)

Place: VUW Law School (Old Government Buildings), Room GBLT4 (1st floor, north wing at back)

Abstract:
Age-structured population projections are used extensively in population dynamic studies and in risk assessment, and capture-recapture methods may be used to provide survival rate estimates. However, the age of an animal first captured as an adult will usually not be known.
We construct likelihood-based models which allow for uncertainty of birth time. Age-dependent hazard rates and senescence may be modelled, and appraised by AIC or likelihood ratio tests.
These models are well suited to isolated populations (with little or no immigration), or to species with high site fidelity after a juvenile dispersal phase. An application that uses the possum data set from the Orongorongo Valley is given.
The same models are also applicable if “birth” is immigration and “death” is emigration, and negligible actual births and deaths occur. This is the situation with migratory birds, which stop over at a site to build up body reserves before continuing the journey. If the best predictor of the current probability of imminent departure is time since arrival, this should be included in the model, even though the exact arrival time is unknown.

 


18 April 2007 (6pm), Stephen E. Fienberg

Speaker: Stephen E. Fienberg, Department of Statistics, Machine Learning Department, and Cylab, Carnegie Mellon University, Pittsburgh, PA 15213, U.S.A.

Title: When Did Bayesian Inference Become “Bayesian”?

Time: Wednesday 18 April 2007, refreshments at 5:30 pm, talk at 6pm

Place: McLaurin Theatre MCLT102, Kelburn Campus

Abstract:
While Bayes’ theorem has a 250-year history, and the method of inverse probability that flowed from it dominated statistical thinking into the twentieth century, the adjective “Bayesian” was not part of the statistical lexicon until relatively recently. This talk provides an overview of key Bayesian developments, beginning with Bayes’ posthumously published 1763 paper and continuing up through approximately 1970, including the period of time when “Bayesian” emerged as the label of choice for those who advocated Bayesian methods.

 


18 April 2007 (Noon), Stephen E. Fienberg

Speaker: Professor S.Feinberg, Maurice Falk Professor of Statistics and Social Science, Carnegie Mellon University

Title: Bayesian Mixed Membership Models for Soft Clustering

Time: 12:00pm, 18 Apr 2007 (Wednesday)

Place: Seminar Room, Cotton 431, Victoria University of Wellington

Abstract :
In many problem settings involving clustering and classification, units can conceivably belong to multiple group. Bayesian mixed membership models provide a natural way to address such “soft” clustering and classification problems. These models typically rely on four levels of assumptions: population, subject, latent variable, and sampling scheme. Population level assumptions describe a general structure of the population that is common to all subjects. Subject level assumptions specify the distribution of observable responses given the population structure and individual membership scores. Membership scores are usually unknown and hence can also be viewed as latent variables which can be treated as fixed or random in the model. Finally, the last level of assumptions specifies the number of distinct observed characteristics (attributes) and the number of replications for each characteristic. We describe four applications of mixed membership modeling: (i) to disability indicators from the National Long Term Care Survey, (ii) abstracts and bibliographies of research reports in The Proceedings of the National Academy of Sciences, (iii) genetic SAGE libraries, and (iv) protein-protein interactions in yeast (this involves extensions that incorporate stochastic block-modeling). Our methods include the computation of full posterior distributions as well as various forms of variational approximations. In the examples, we also discuss issues of model assessment and specification.

 


16 April 2007, Stephen E. Fienberg

Speaker: Professor S.Feinberg, Maurice Falk Professor of Statistics and Social Science, Carnegie Mellon University

Title: Making Forensic Science More Scientific: Statistics and the Evaluation of Forensic Evidence

Time: 12:00pm, 16 Apr 2007 (Monday)

Place: Railway West Wing, Victoria University of Wellington

Abstract:
In the US, forensic science is under increasing attack. This is the consequence of the confluence of a number of elements including (a) continued revelations of wrongful convictions linked to faulty forensic evidence, (b) the resounding success of DNA and other genetic evidence in a forensic context, and (c) the “CSI Effect”—the expectation of infallible high tech forensic tools that are part of the popular weekly crime show, Crime Scene Investigation. In this talk I will describe a potpourri of forensic tools (e.g., the polygraph, eyewitness testimony, traditional fingerprinting, and new computer forensic tools), legal cases in which they arise, and the role statistics plays in their evaluation and legal credibility.


22 March 2007, Richard Arnold

Speakers: Richard Arnold and John Townend, Victoria University of Wellington

Title: Using earthquakes to measure stress in the earth’s crust

Time: 6:00pm, Thursday 22 March 2007 (light refreshments from 5:30pm)

Place: VUW Law School (Old Government Buildings), Room GBLT4

Abstract:
When an earthquake occurs a planar weakness in the rocks of the earth’s crust (a fault) is overwhelmed by the ambient stresses (pressures), and the rocks on one side of the fault slide, releasing seismic waves. The direction of the slip and the orientation of the fault plane on which the slip happens contain information about the nature of the stresses which caused the earthquake. The information about the stress provided by a single earthquake is very weak, but many separate earthquakes can be used to constrain the stress parameters more strongly. This talk will present a new Bayesian solution to extracting information about the stress which drives earthquakes.


28 November 2006, Nanny Wermuth

Speaker: Nanny Wermuth, Chalmers/Gothenburg University, Sweden

Title: Distortions of effects

Time: 6:00pm, Tuesday 28 Nov 2006

Place: Lecture Theatre 3, Ground Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
Unnoticed confounding may severely distort the direction and strength of the effect of an explanatory variable on its response variable, as given by a stepwise data generating process. For direct confounding this effect is known. If it arises from a common unobserved explanatory variable, it is relevant mainly for observational studies, since it is avoided by successful randomization. By contrast, indirect confounding, which is discussed now, is an issue also for intervention studies. For general stepwise generating processes, we provide matrix and graphical criteria to decide which types of direct or indirect confounding may be present and when they are absent.


22 November 2006, Estate Khmaladze

Speaker: Estate Khmaladze, Victoria University of Wellington

Title: On distributions that do not follow asymptotic theory and other anomalies

Time: 6:20pm, Wednesday 22 Nov 2006

Place: Lecture Theatre 3, Ground Floor, Rutherford House, 23 Lambton Quay

Abstract:
It is so interesting to calculate or simulate things in probability and statistics that our science has almost been converted into a sort of experimental science. However, the most interesting such calculations are when, instead of showing how great the theory is, they disagree with mathematical statements. In cases like this we typically do not understand the phenomena enough or our intuition is somewhat conservative and, hence, there is a chance of discovery.
In the talk we present two phenomena of this kind. One is exact values for non-crossing probabilities for finite samples and their limit. We will argue that we do not understand enough the tails of empirical distributions. In other words, we do not understand enough the Law of the Iterated Logarithm: one of the basic laws of probability and statistics. The second is another look on samples and likelihood ratios. We illustrate the unusual yet typical behaviour of ordinary likelihood ratio statistics, for samples of size n=100, and even n=20.
The material of the first part can be found in the speaker’s joint paper with a former PhD student, Eka Shinjikashvili: J. Appl. Prob., 2002. For the illustrations in the second part we are indebted to the curiosity of Nick Webb, a current VUW Graduate student.


1 November 2006, Len Cook

Speaker: Len Cook, Former NZ Government Statistician (1992–2000) and Head of the UK Office for National Statistics, the Registrar General of England and Wales, and the first UK National Statistician (2000–2005)

Title: What might official statistics in the Antipodes learn from the British statistical system, and vice versa?

Time: 6:00pm, Wednesday 1 Nov 2006

Place: Lecture Theatre 3, Ground Floor, Rutherford House, 23 Lambton Quay

Abstract:
Over the past sixty years, the UK, Australia and New Zealand have had quite different approaches to the organisation of official statistics, but these differences are now diminishing. The forces we face in common are now the more critical determinants of performance. Antipodean institutions can learn from the responsiveness of the UK statistical system, while the UK has long needed the stronger focus on investment of both New Zealand and in particular Australia. The UK environment is a tough one, and the quest for broader robust and timely solutions exists in more fields than in the Antipodes, partly because of the size of the UK, and the extent of its analytical history.
We are well equipped to share more, as a global media, international collaboration in research and global convergence of policy settings demand coherence nationally, regionally and now globally in statistical practice.


12 October 2006, Dimitar Christozov and Stefanka Chukova

Speakers: Dimitar Christozov, American University in Bulgaria; and Stefanka Chukova, Victoria University of Wellington

Title: Estimation of the mean cumulative function from automotive warranty data: a stratification approach

Time: 6:00pm, Thursday 12 October 2006

Place: Lecture Theatre 3, Ground Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
This study deals with a type of truncation that occurs with typical automotive warranties. Warranty coverage and the resulting claims data are limited by mileage as well as age. Age is known for all sold vehicles all the time, but mileage is only observed for a vehicle with a claim and only at the time of the claim. Here we deal with the univariate case, taking either age or mileage as the usage measure. We evaluate the mean cumulative number of claims or cost of claims and its standard error as functions of the usage measure. Within a nonparametric framework, we extend the usual methods in order to account for the fact that the odometer readings are available only for a vehicle with a claim and only at the time of the claim. We illustrate the ideas with real data on four cases based on whether the usage measure is age or miles and whether the results are adjusted for withdrawals from warranty coverage. This study is an extension of Chukova and Robinson’s (2005) findings. Firstly, we weaken their assumption of having a linear relationship between the mileage accumulation and age of a car and, secondly, our model accounts for multiple claims whereas the previous model was based on the last claim only.
Reference: S. Chukova, J. Robinson (2005). Estimating mean cumulative functions from truncated automotive warranty data. Modern Statistical and Mathematical Methods in Reliability, Eds. A. Wilson, N. Limnios, S. Keller-McNulty, Y. Armijo, World Scientific, Singapore, 2005, pp.121–135.


25 July 2006, Edith Hodgen, Rachel Dingle and Hilary Ferral

Speakers: Edith Hodgen, Rachel Dingle and Hilary Ferral, New Zealand Council for Educational Research

Title: Statistics: a growth area for NZCER

Time: 6:00pm, Tuesday 25 July 2006

Abstract:
The New Zealand Council for Educational Research (NZCER) has been in existence for 72 years, but it is only for the last four that the council has employed at least one statistician. Having started with one, we have appointed an additional statistician almost every year since then.
We plan to outline the range of work carried out at NZCER, some of the challenges faced by those doing quantitative research in New Zealand schools, some of our emerging areas of excellence, and a few case studies.


20 June 2006, Ian Westbrooke

Speaker: Ian Westbrooke, Research Development and Improvement Division, Department of Conservation, Christchurch

Title: Meeting statistical needs in a conservation management organisation

Time: 6:00pm, Tuesday 20 June 2006

Place: Lecture Theatre 3, Old Government Buildings, 15 Lambton Quay

Abstract:
DOC is responsible for all New Zealand’s conservation estate and for conserving native ecosystems and biodiversity, including threatened species. To carry out such diverse management roles effectively, scientific input is essential. We have around 60 national science staff, plus a number working as technical staff in the 13 conservancies and on other projects. I joined in 2000 in the newly-created position of statistician.
I plan to describe the range of scientific work at DOC and show some examples from land, marine and social areas. I will outline what I see as key statistical needs at DOC, how some of those needs are currently being met, and how those with statistical skills can assist conserving NZ’s native biodiversity. One task is encouraging and empowering staff throughout DOC to analyse the vast piles of unanalysed monitoring and other observational data. Encouraging the use of Excel and statistical packages to explore data and pose management questions can lead to significant gains. For more formal studies, design and analysis issues raise a huge range of statistical questions.


16 March 2006, Geoff Chambers

Speaker: Geoff Chambers, Cell and Molecular Biosciences, Victoria University of Wellington

Title: Out of Taiwan? Genetics sheds new light on Maori origins

Time: 6:00pm, Thursday 16 March 2006

Place: Lecture Theatre 1, Old Government Buildings, 15 Lambton Quay

Abstract:
The migration into and settlement of remote Oceania by the modern Polynesian and Maori peoples is a significant achievement, which has been the subject of extensive research and scholarship. The routes taken by the Austronesian peoples and the origins of the migrations are subject to ongoing debate. We present a range of findings from molecular genetic studies of Polynesian and New Zealand Maori populations and a synthetic total evidence theory that we suggest can account for key elements of the migrations.
Note: This talk is based on a paper presented at the International Symposium on The Dispersal of Austronesians and the Ethnogenesis of the People in the Indonesian Archipelago (Chambers, 2005); published in NZ Science Review 63: 75–80.


13 December 2005, Rod Lea

Speaker: Rod A Lea, Senior Scientist, ESR

Title: Genome Informatics and Disease Susceptibility

Time: 6.00pm, Tuesday 13 December 2005

Place: Lecture Theatre 3, Old Government Buildings, 15 Lambton Quay

Abstract:
The advances in biotechnology over the past decade have resulted in the production of an enormous quantity of molecular data. Currently there are major research efforts worldwide to develop statistical computing methods capable of extracting meaning from large, complex molecular genetic datasets (genome informatics). This seminar will overview the field and provide some examples of how statistics are used to understand the genetics of complex disease in humans.


8 November 2005, Tony Vignaux

Speaker: Tony Vignaux, Emeritus Professor of Operations Research, VUW

Title: Incorporating factors such as Chance and Risk

Time: 6.00pm, Tuesday 8 November 2005 (light refreshments from 5.30pm)

Place: Lecture Theatre 2, Old Government Buildings, 15 Lambton Quay

Abstract:
A description of personal encounters with decision situations involving chance and risk. This will include practical examples of some of: sensitivity analysis, queue theory, simulation, game theory, stock control, investment analysis, decision analysis, dimensional analysis, and genetic algorithms.
Deterministic OR and straightforward statistics, including Bayesian methods, will be ignored in this talk.


14 September 2005, Paul Jose

Speaker: Paul Jose, School of Psychology, VUW

Title: Making Moderation and Mediation Quick, Easy, and Clear

Time: 6.00pm, Wednesday 14 September 2005 (light refreshments from 5.30pm)

Place: Lecture Theatre 2, Old Government Buildings, 15 Lambton Quay

Abstract:
At present there is considerable confusion about how and when to do moderation and mediation. Statistics textbooks discuss moderation and mediation as special cases of ANOVA and multiple regression respectively, but these two techniques are rarely discussed in the same context in these books. In my research in developmental, social, and clinical psychology I often use both methods, sometimes on the same datasets. In my teaching (research methods in psychology) I promote the use of these two techniques. My overwhelming response from students and academicians is one of interested ignorance. One staff member asked me “what button do I push in SPSS to make moderation happen?”. My second insight about this area is that current statistical packages (like SPSS) do not perform either moderation or mediation easily and cleanly.
This situation has led me to create two Excel macros that permit a user to take output from a stat package like SPSS and within minutes generate publication-ready figures. Recently we have rewritten these programmes in HTML and have made them available free of charge on my home page. Plans are afoot for a stand-alone programme that will conduct both of these techniques from raw data.
My presentation will be a basic discussion of the statistical techniques of moderation and mediation as well as a demonstration of my two programmes, ModGraph and MedGraph. Interested parties may wish to view my home page before the lecture to gain a deeper understanding of these programmes and techniques: http://www.vuw.ac.nz/psyc/staff/paul-jose/index.aspx.


2 August 2005, Phil Lester

Speaker: Phil Lester, School of Biological Sciences, VUW

Title: Using discriminant analysis to predict the establishment success of exotic ant species in New Zealand

Time: 6.00pm, Tuesday 2 August 2005 (light refreshments from 5.30pm)

Place: Lecture Theatre 2, Old Government Buildings, 15 Lambton Quay

Abstract:
Biological invasions can dramatically alter ecosystems. An ability to predict the establishment success for exotic species is important for biosecurity and conservation purposes. Using discriminant analysis I examine the exotic New Zealand ant fauna for characteristics that predict or determine an exotic species’ ability to establish. Quarantine records show interceptions of 66 ant species: 17 of which have established, 43 have failed to establish, whereas nests of another six are periodically observed but have failed to establish permanently (called ‘ephemeral’ establishment). Mean temperature at the highest latitude and interception variables were the only factors significantly different between established, failed or ephemeral groups. Aspects of life history, such as competitive behaviour and morphology, were not different between groups. However, in a stepwise discriminant analysis, small size was a key factor influencing establishment success. Interception rate and climate were also secondarily important. The resulting classification table predicted establishment success with 71% accuracy. Because not all exotic species are represented in quarantine records, a further discriminant model is described without interception data. Though with less accuracy (65%) than the full model, it still correctly predicted the success or failure of four species not used in the previous analysis. Despite the low estimated accuracy, Malahanobis distances from this model were used to successfully predict the status of five ant species not used in the above analysis. Predicting which species will establish in a new area appears an achievable goal, which will be a valuable tool for conservation biology.


19 May 2005, Statistical Education

Speakers: Four 10-minute talks, as outlined below, followed by up to 45 minutes of discussion among presenters and the audience

Title: Into uncharted waters: school statistical education from 2005 onwards

Time: 6.00pm, Thursday 19 May 2005 (light refreshments from 5.30pm)

Place: Lecture Theatre 2, Old Government Buildings, 15 Lambton Quay

Abstract:
Alex Neill (NZCER) will introduce and chair the meeting, as current convenor of the Education Committee of the NZ Statistical Association.
The session has been devised collaboratively by the Education Committee, NZSA and the Wellington Maths Association (WMA) for two sets of people: Wellington mathematics teachers and Wellington statisticians.
The purpose is to update both groups on recent and impending changes to statistics in schools. There are major possibilities and risks for statistics within school mathematics. We hope to create discussion and plans about how the two sets of people can work together, to help ensure that the future for statistical education is useful and exhilarating for teachers, students and the statisticians who assist them.
There will be four 10 minute presentations:

  1. Mike Camden, Statistics New Zealand: The status of the mathematics and statistics part of the current revitalisation of the school curriculum, and the potential for a paradigm shift in mathematics education.
  2. Alasdair Noble, Massey University: The current review of the one-year-old NCEA Level 3 and Scholarship Standards.
  3. Terry McAuliffe, Tawa College: Statistics in NCEA Mathematics at Levels 1, 2 and 3: victories and challenges.
  4. David Vere-Jones, SRA Ltd and VUW: Changes afoot in the UK and Australia.

The discussion will be led off by Megan Clark (VUW) and Robin Averill (WCE), and will focus on the question: How can the statistical community work with teachers, to make their task lighter and more enjoyable, now and in the future?


13 April 2005, Mark Weatherall

Speaker: Mark Weatherall, Wellington School of Medicine and Health Sciences; Joint work with R.M. Pickering and S. Harris, Health Care Research Unit, University of Southampton, UK

Title: Graphical sensitivity analysis with different methods of imputation for a trial with probable non-ignorable missing data

Time: 6.15pm, Wednesday 13 April 2005 (light refreshments from 5.45pm)

Place: Lecture Theatre 4, First Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
Graphical sensitivity analyses have recently been recommended for clinical trials with non-ignorable missing binary outcome. We demonstrate an adaptation of this methodology for a continuous outcome of a trial of three cognitive-behavioural therapies for mild depression in primary care, in which one arm had unexpectedly high levels of missing data. Fixed value and multiple imputation from a normal distribution (assuming either varying mean and fixed SD, or fixed mean and varying SD) were used to obtain contour plots of the contrast estimates with their P values superimposed; their confidence interval; and the root mean square error. Imputation was based on both the outcome value alone, or on change from baseline. The plots showed fixed value imputation to be more sensitive than imputing from a normal distribution, but the normally distributed imputations were subject to sampling noise. The contours of the sensitivity plots were close to linear in appearance with the slope approximately equal to the ratio of the proportions of subjects with missing data in each trial arm.


24 February 2005, Tim Ball

Speaker: Tim Ball, Statistical Consulting for Continuous Improvement

Title: Golden Opportunities – A Case Study

Time: 6.15pm, Thursday 24 February 2005 (light refreshments from 5.45pm)

Place: Lecture Theatre 3, Ground Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
As a commercial statistical consultant, I view my most important role as one of education – helping my client long-term improve their operations, rather than just doing a “good” statistical study for the immediate project on hand. I will illustrate this talk with examples from my work with a company that produces gold ore reference materials – covering statistical and practical problems and aspects of the work done with the client during our, so far, 7+ years of cooperation. The talk will be high in pictorial content, and low in mathematics. It will also contain some interesting facts about the production and measurement of gold. I hope to get over the thrill I get, as a consultant, in discovering new things about fields in which I have only layman knowledge.


7 December 2004, Estate Khmaladze

Speaker: Estate Khmaladze, Victoria University of Wellington

Title: Probability and Statistics in Tbilisi, Georgia in retrospect: 1963-1983

Time: 6pm, Tuesday 7 December 2004 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Ground Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
Georgian Mathematics, from the very beginning of the 20th century, was strong – one of the strongest schools within the Soviet Union, at any rate. But it was mostly mechanics, elasticity theory, mathematical physics and complex variables, functional analysis and differential equations, and also strong topology and algebra.
Probability theory and statistics took root in Georgia much later. One can start with the famous Tbilisi Conference of 1963, or earlier – from the mid 1930s, with the course of lectures of Razmadze and frequent visits of Kolmogorov and P.S. Alexandrov. How these sciences developed since then in Georgia, and what was the level and forms of statistical life – that is what the talk will try to present. We will look also on scientific and personal connections, and frequent meetings with Kolmogorov, or Smirnov, or – from a younger generation – with Prohorov or Bolshev, Skorohod or Shiryaev, Ibragimov or Gnedenko.
One aspect that is always so interesting is the human aspect: this huge amount of great, sparkling talents of individuals, which often is somehow hidden and passes almost unnoticed by an outside observer, but which has to be there and is so inspiring and beautiful. I will speak about a few individuals as well. We will dwell a little bit upon how the interest in applications, this most important intrinsic feature of any good research in our science, manifested itself on Georgian ground, but had only little prospect in Soviet times.
All this will be personal recollections of the speaker, presented, however, in the hope that there are some common features, or some very specific features, which will be interesting to look at for others.


18 November 2004, Robin Willink

Speaker: Robin Willink, (Applied Mathematics) Industrial Research Ltd

Title: Statistical methods in metrology (measurement science)

Time: 6pm, Thursday 18 November 2004 (light refreshments from 5.30pm)

Place: Lecture Theatre 2, Old Government Buildings, 15 Lambton Quay

Abstract:
Scientists at the Measurement Standards Laboratory of New Zealand (MSL), which forms part of Industrial Research Ltd., are responsible for maintaining New Zealand’s standard units (such as the kilogram, second and metre) to ensure `traceability’ to the standards of other countries. They also carry out research in measurement science and conduct commercial calibration work. This talk will summarize research that I have carried out over the last five years through links with scientists at MSL. Issues I will discuss will include:

  1. the calculation of a reference value for an artefact measured in a comparison involving the corresponding laboratories in many countries,
  2. the `degree-of-equivalence’ summarizing the difference between the results of any two laboratories,
  3. the way in which the metrology community are encouraged to evaluate and express the potential error in any measurement estimate.

Much can, and probably will, be said about the need for practical methods, the room for clear communication to metrologists (who are predominantly physicists), and the interpretation of probability. The issue of the best way to combine systematic and random errors is still alive – although these terms, and even the term ‘error’, are out of favour. Academic statisticians might get a shock!


30 September 2004, Robert Davies

Speaker: Robert Davies, Statistics Research Associates Limited

Title: Crash Risk and Road Surface Characteristics

Time: 6pm, Thursday 30 September 2004 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Ground Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
New Zealand’s state highways are surveyed annually and surface characteristics such as roughness, skid resistance and rutting are recorded at either 10 or 20 metre intervals. Curvature and gradient are also recorded. The analysis described in this presentation relates the road vehicle crash-rate to the road surface and geometry data. The eventual aim is to find cost effective measures for reducing the crash-rate through highway improvements. The main analysis method is a variant of Poisson regression. Particular problems that need to be handled by the analysis include the volume of data involved, the errors in crash location, the questionable nature of some of the data and the inevitable incompleteness of the data. Nevertheless the analysis suggests that useful and credible results can be obtained.


27 May 2004, Jeff Robinson

Speaker: Jeff Robinson, General Motors R&D Center, Michigan USA

Title: Estimating Mean Functions from Warranty Data with Dual Useage Measures

Time: 6pm, Thursday 27 May 2004 (light refreshments from 5.30pm)

Place: Lecture Theatre 2, Old Government Buildings, 15 Lambton Quay

Abstract:
This talk summarizes some practical estimation problems that occur in the analysis of typical automotive warranty data. Warranty coverage and the resulting claims data are limited by mileage as well as age. Age is known for all sold vehicles all the time, but mileage is only observed for a vehicle with a claim and only at the time of the claim. So an unknown number of vehicles leave coverage due to the mileage constraint, and the number of vehicles eligible to generate a claim at any age-mileage combination is subject to uncertainty. The latter problem makes a full bivariate treatment of this problem challenging. Here we concentrate on univariate solutions (for both age and mileage) that account for the mileage truncation. We take a nonparametric approach, so the methods are extensions of the usual calculations for the mean cumulative number of claims or cost of claims and its standard error (Nelson, 2003). We extend slightly applications suggested by Hu & Lawless (1996 JASA) for dealing with mileage withdrawals, and simultaneously address the problem of claim reporting delay first discussed by Kalbfleisch, Lawless and Robinson (1991). Real automotive warranty data examples illustrate the methods.


29 April 2004, James Liu

Speaker: James Liu, Victoria University of Wellington

Title: Dynamics of interpersonal political environment and party identification: longitudinal studies of voting in Japan and NZ

Time: 6pm, Thursday 29 April 2004 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Ground Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
Panel data over the course of a year examined the longitudinal dynamics between social networks, social identifications, and voting behavior among a general sample of registered voters in Wellington New Zealand and a national sample in Japan. Stability in the interpersonal political environment (or the political preferences of a person’s social network) was predicted independently by stability of party identification (or social identity with political party) and lower education in Japan; whereas stability in party identification was predicted by stability of interpersonal political environment and age in both countries. Stability of party identification predicted voting consistency in both countries, whereas stability of interpersonal political environment made an independent contribution to voting consistency in Japan only. There were cultural differences in levels of interpersonal political environment stability. Results provided support for the dynamical systems theory of groups, which claims that interpersonal political environment and party identification are dynamically interrelated to provide heuristics under uncertainty.
Key words: dynamics of voting, interpersonal environment, party identification, Japan, New Zealand.


25 March 2004, Shirley Pledger

Speaker: Shirley Pledger, Victoria University of Wellington

Title: Using finite mixtures to model heterogeneity in capture-recapture models

Time: 6pm, Thursday 25 March 2004 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Ground Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
Capture-recapture models for both open and closed populations are bedevilled by estimator bias caused by assuming individuals are homogeneous in their survival and capture probabilities. Although all models are wrong, some which use finite mixtures to allow for individual heterogeneity are providing worthwhile bias reduction.
We pretend the animals come from finitely many classes with unknown membership lists, and assume homogeneity within classes. If heterogeneity is present, this provides better fitting models, less biased estimates of parameters (e.g. abundance) and better confidence interval coverage than the assumption of overall homogeneity, but at the price of less precision.
Some models and results from both closed and open populations will be discussed.


11 February 2004, Brian Easton

Speaker: Brian Easton

Title: The Estimation, Use and Misuse of Household Equivalence Scales

Time: 6pm, Wednesday 11 February 2004 (light refreshments from 5.30pm)

Place: Lecture Theatre 4, First Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
Household Equivalence Scales are used to adjust the incomes of households of different composition to equivalent (material) standards of living. The simplest is to adjust them on a per capita basis, but this does not allow for either economies of scale or that children have different requirements to adults.
Brian Easton created his first scale thirty years ago. Last year, as a part of their report on Health and Household Economy Project, he and Suzie Ballantyne included a chapter which is the most comprehensive review of the work done in New Zealand. It showed that the scales in New Zealand have little scientific validity, and that different scales have quite different outcomes for practical matters such as to the level and the composition of poverty.
The presentation will be a tribute to Claudio Michelini, of Massey University, who died unexpectedly in 2000, while working on the most scientific household equivalence scales we have available.
See Also: Household Equivalence Scales
http://www.eastonbh.ac.nz/modules.php?name=News&file=article&sid=460,
Validation and the Health and Household Economy Project
http://www.eastonbh.ac.nz/modules.php?name=News&file=article&sid=229,
and Claudio Michelini
http://www.eastonbh.ac.nz/modules.php?name=News&file=article&sid=228.


26 November 2003, Stefanka Chukova and Yu Hayakawa

Speaker: Stefanka Chukova and Yu Hayakawa, Victoria University of Wellington

Title: Warranty analysis: An overview and some new probabilistic models

Time: 6pm, Wednesday 26 November 2003 (light refreshments from 5.30pm)

Place: Lecture Theatre 4, First Floor, Old Government Buildings, 15 Lambton Quay

Abstract:
In today’s market, product warranty plays an increasingly important role in both customer and commercial transactions. The use of warranties is widespread and they serve many purposes, including protection for manufacturers, sellers, and buyers. They are also signals of quality and elements of marketing strategy.
In this talk, firstly we will focus on a detailed taxonomy for mathematical models of one-dimensional warranty, introduce the idea of degree of repair, and discuss the extension to two- dimensional warranty and related problems. Secondly, we will present a specific warranty model. The cost of each warranty claim depends on the non-zero length of the repair time. Two types of free replacement warranty policies are considered: non-renewing and renewing. An alternating renewal process is employed to model the operating and repair times. New results for alternating renewal processes in a finite horizon are derived. These results are used to evaluate the warranty costs over the warranty period and over the life cycle of the product under both types of policies.


28 October 2003, Nick Longford

Speaker: Nick Longford, De Montfort University, Leicester, UK

Title: Stability of household income in European countries in the 1990s and a NZ connection

Time: 6pm, Tuesday 28 October 2003 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Old Government Buildings, 15 Lambton Quay

Abstract:
The talk explores the patterns of change in the annual household income in the countries of the European Community during the years 1994–1999. The income is modelled by mixtures of log-normal distributions, and the mixture components are interpreted as representing one sub-population with steady increments and others with various levels of volatility. The method is extended to models for a combination of log-normal and categorical variables. An index of income stability is defined for the countries. Graphical summaries of the results are emphasized.
Current and planned research in another application of mixture models is outlined and some results about the local-area house-price inflation in New Zealand are presented.
Coauthors: M.G. Pittau (University of Rome ‘la Sapienza’, Rome, Italy)


14 August 2003, Caroline Roughneen

Speaker: Caroline Roughneen, Trinity College, Dublin

Title: Study of Engineering as a Career Choice

Time: 6pm, Thursday 14 August 2003 (light refreshments from 5.30pm)

Place: Lecture Theatre 4, Old Government Buildings, 15 Lambton Quay

Abstract:
Recent research shows that engineering as a career choice is in decline in Ireland. This talk will examine the determinants that attract female students, in particular, into engineering studies at tertiary level. It will also identify obstacles to female students applying for and enrolling in engineering courses and suggest practical measures that would lead to a more equitable balance between men and women.
The methodology includes two national surveys in Ireland and one national survey in New Zealand. These surveys are targeted at Careers Advice teachers in Ireland and final year students in both countries. The study will establish the availability and usefulness of engineering career information provided by engineering firms, tertiary level institutes and the engineering professional body. The information provided by this study will be used to develop best practices to promote engineering courses at tertiary level and identify measures or marketing strategies that would best interest female students in careers in engineering.


9 July 2003, Mark Weatherall

Speaker: Mark Weatherall, Wellington School of Medicine and Health Sciences

Title: Prevention of falls and fall related fractures in community dwelling older adults: A meta-analysis of estimates of effectiveness based on recent guidelines

Time: 6pm, Wednesday 9 July 2003 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Rutherford House, 23 Lambton Quay

Abstract:
Background: Two recent falls prevention guidelines have been published but did not include quantitative estimates of effectiveness based on the literature that was reviewed to support their recommendations.
Aims: To produce quantitative estimates of effectiveness of falls prevention programmes from the randomised controlled trials cited in the guidelines together with an updated literature search to August 2002.
Methods: Meta-analysis of randomised controlled trials cited in falls guidelines and studies identified by an updated literature search. Randomised controlled trials were identified from the falls guidelines and a literature search which met the following criteria: Trials in community dwelling older people, one year follow up, and outcome measures reported as number of subjects with at least one fall or number of subjects with a fracture.
Results: The guidelines identified four studies of ‘Exercise as a sole intervention’ which when combined with one further study identified on the literature search gave a fixed effects odds ratio favouring this strategy of 0.81 (95% CI 0.58 to 1.14), number needed to treat to prevent one person having a fall 19.5. The guidelines identified seven studies of a ‘Multiple intervention’ strategy that gave a random effects odds ratio favouring this strategy of 0.64 (95% CI 0.47 to 0.88). Four further studies were identified by the literature search. The updated odds ratio favouring this intervention strategy was 0.65 (95% CI 0.52 to 0.81); number needed to treat was 9.8. Only two studies had data for fracture and a fixed effect odds ratio favouring falls interventions for fracture prevention was 0.50 (95% CI 0.18 to 1.4), number needed to treat to prevent one person having a fracture 45.5.
Conclusion: Semi-quantitative statements of evidence can both understate and overstate the effectiveness of falls prevention strategies. There is moderate evidence of efficacy for fall prevention particularly for multiple intervention strategies.


11 June 2003, Leigh Bull

Speaker: Leigh Bull, DOC

Title: Sizing up shearwaters: morphological variation in the genus Puffinus

Time: 6pm, Wednesday 11 June 2003 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Rutherford House, 23 Lambton Quay

Abstract:
The shearwater genus Puffinus was used to investigate how the interactions between an organism and its environment are manifested in its morphology. This study represents one of the few comprehensive analyses of size variation in seabirds, and the first for Puffinus. Three levels of morphological variation were investigated: interspecific differences between species, sexual size dimorphism between the sexes, and intraspecific geographic variation over a species range. Multivariate statistical techniques such as canonical discriminant analysis and MANOVAs were used to quantify the patterns of morphology in the shearwater genus Puffinus. Differences in phenotypic variation among traits and between sexes, as measured by the coefficient of variation, were used to investigate the possible mode and intensity of selection operating on each trait and sex respectively. Correlations were calculated to investigate the possible relationships between the morphology and ecological variables such as food, insularity and climate. Food, through its influence on competition, dispersal, growth, fecundity and survival, appears to play an important role in the relationship between the morphology and ecology of Puffinus individuals.


1 May 2003, Chris Francis

Speaker: Chris Francis, NIWA (coauthor: Bryan Manly, WEST Inc, Cheyenne, Wyoming)

Title: Simultaneous testing for mean and variance differences with nasty data

Time: 6pm, Thursday 1 May 2003 (light refreshments from 5.30pm)

Place: Lecture Theatre 101, Murphy building, Kelburn Parade

Abstract:
Possibly the most commonly performed type of statistical test is for differences in means. It is often advisable to precede such a test by another test for differences in variances because the mean-tests commonly perform poorly in the presence of such differences. We describe an approach, based on randomization, that tests for both these differences, and evaluate its performance via a simulation experiment.
The approach is shown to be useful as a robust, conservative method in cases when the samples come from very non-normal distributions. One possible outcome of the test is the conclusion that there are mean and/or variance differences, but it is not possible to say which.


27 March 2003, Srinivas Chakravarthy

Speaker: Srinivas Chakravarthy, Professor of Operations Research and Statistics, Kettering University, Flint, Michigan, USA

Title: Impact of worker cross-training in service systems

Time: 6pm, Thursday 27 March 2003 (light refreshments from 5.30pm)

Place: Lecture Theatre 101, Murphy building, Kelburn Parade

Abstract:
We consider a service system with two types of customers. In such an environment the servers could either be specialists who can serve a specific customer type or generalists who can serve either type of customers. Although cross-trained workers are more flexible and help reduce system delay, they also contribute to the increased costs and reduced service efficiency. The objective of this paper is to provide insights into the choice of a right workforce mix of flexible and dedicated servers that minimizes the system related costs. Matrix-analytic methods are used in this study.


17 October 2002, Frances Krsinich and Mike Camden

Speakers: Frances Krsinich and Mike Camden, Statistics New Zealand

Title: The use of noise to confidentialise tables

Time: 6pm, Thursday 17 October 2002 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Rutherford House, 23 Lambton Quay

Abstract:
SNZ confidentialises tables of magnitude data (e.g. total turnover for industry by region) by first identifying sensitive cells for suppression using a dominance rule and then performing secondary cell suppressions to prevent derivation of the sensitive cells from marginal totals. Although this is the approach adopted by most statistical agencies, it has some significant limitations – secondary cell suppression is time-consuming and results in the suppression of non-sensitive data.
The US Census Bureau recently proposed a new approach – unbiased perturbation of the sampling weights such that ‘noise’ in the resultant confidentialised table is targetted towards the sensitive cells. This approach is much simpler to apply than cell suppression and, arguably, results in less overall information loss. We have been researching the application of this method to the Annual Enterprise Survey, and hope to introduce it in 2003.
In the course of this work, we have identified a possible generalisation of the method to tables of count data, such as those produced from the Population Census. For some customised outputs, such as bulk outputting of many related tables of census data, this may be a more appropriate method to use than random rounding to base 3, the current method for tables of counts from Census.
In this talk, we will outline the reasons for confidentialising data, and list some existing methods. We will detail the version of the noise method that SNZ hopes to implement for tables of magnitude data, then discuss how a noise method for tables of count data could work, and what we would need to do to assess it.


27 August 2002, Paul Dyer

Speaker: Paul Dyer, Head of Investment Strategy, AMP Henderson, Wellington

Title: Are financial markets predictable? Some implications for investors

Time: 6pm, Tuesday 27 August 2002 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Old Government Buildings, 15 Lambton Quay


24 July 2002, Jean Thompson

Speaker: Jean Thompson, JAD Associates, Wellington

Title: ‘Real world’ statistical data and the role of the consultant statistician

Time: 6pm, Wednesday 24 July 2002 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Old Government Buildings, 15 Lambton Quay

Abstract:
At the beginning of 1962 when I joined the Applied Maths Laboratory of the DSIR in Wellington, the statistical work I got involved in substantially comprised helping various agricultural, biological and ecological scientists analyse their data. I was to learn quickly that unless the statistician had a part in designing the data collection system, even exhaustive and highly-sophisticated analysis could often yield little new information. Sadly, in essence, not much has changed in the intervening 40 years.
There is still a perception in many quarters that the statistician is the “necessary evil” to get the data analysed and frequently they are not consulted until long after an investigation is well under-way. This is a great shame, for while huge advances have been made in the methods we can use to analyse data and the facility with which it can be done, there is still the vexatious issue of data quality. In the ideal world one would be part of the whole process but it is more usual for a consultant to be brought in late in the day often after much damage has been done. However, we must be careful not to necessarily blame the investigator for hard-to-handle data. Some areas of application simply do not produce nice clean data no matter how one tries, even with good input from a statistician.
It was a good 20 years ago that the Applied Maths Division of the DSIR started commercial consulting and thereby opened the floodgates for highly variable data. After its demise in 1992 I continued as a private consultant doing the same sort of things I had been doing for my public sector employers, helping researchers and people in business understand the processes they cared about.
In this talk I will summarize some of the situations I have encountered over the last 5 years and focus on what I see as important issues for applied statisticians and their teachers.
The philosophy and material I will present was given in a one-hour seminar at the University of Canterbury in April 2001 and also at the NZSA Conference in Christchurch in December 2001.
A panel discussion will follow Jean’s talk, starting at approximately 6.30pm. Jean will be joined on the panel by Robert Davies and Tim Ball, who are both consulting statisticians with considerable experience. The panel will respond to questions from the audience, with the intention of addressing further ‘real world’ statistical experiences.


21 February 2002, Richard Arnold

Speaker: Richard Arnold, Victoria University of Wellington (joint research with Tony Vignaux and Denis Sullivan)

Title: Bayesian spectral analysis of white dwarf light curves

Time: 6pm, Thursday 21 February 2002 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Old Government Buildings, 15 Lambton Quay

Abstract:
White Dwarfs are stars near the end of their lives which may pulsate with periods of a few minutes, and which can be observed to brighten and dim as they pulsate. In this paper a Bayesian approach due to Bretthorst (1988) is applied to the analysis of the light curves of white dwarfs. The method yields estimates of the dominant pulsation frequencies which are highly accurate and superior to estimates obtained from classical Fourier techniques. Moreover, the method can be applied to datasets where there are missing values, where the sampling is not uniform in time, and in particular allows the combination of observations from different observing runs. In this paper we analyse observations of a particular white dwarf on 8 separate occasions over a two year period.


6 December 2001, Brian Bull

Speaker: Brian Bull, National Institute of Water and Atmospheric Research (joint research with Dave Gilbert)

Title: Catch-at-age data from New Zealand fisheries

Time: 6pm, Thursday 6 December 2001 (light refreshments from 5.30pm)

Place: Lecture Theatre 3, Old Government Buildings, 15 Lambton Quay

Abstract:
Catch-at-age analysis estimates the age and size distributions of fish taken by a commercial fishery, based on samples of fish from individual catches. The resulting age frequencies are key inputs to the stock assessment process, which assesses the sustainability of the fishery. Catch-at-age analysis is undertaken for most major New Zealand finfish stocks, including hoki, orange roughy, and snapper. I will talk about the sampling programme and the quirks of the resulting data. The analysis is statistically straightforward but involves several interesting issues, including the choice of stratifying variables, the bootstrapping technique used to calculate the variability of the estimate, and the two competing methods used to convert length distributions to age distributions.


16 October 2001, Dean Hyslop and Dave Mare

Speaker: Dean Hyslop and Dave Mare, The Treasury

Title: Understanding Changes in the Distribution of Household Incomes in New Zealand Between 1983–86 and 1995–98

Time: 16 October 2001

Abstract:
This paper presents an analysis of changes in the distribution of gross household income and income inequality over the period 1983–98. The analysis applies a semiparametric approach to study the effects of changes in the distribution of household types, and changes in National Superannuation (old age pension), household socio-demographic attributes and employment outcomes, and in the “economic returns” to such attributes and employment outcomes on the distribution of income, and uses kernel density methods to estimate these effects. This approach provides a visual appreciation of the shape of the income distribution, and is important in understanding how each of these factors affected different parts of the distribution over the period. We also estimate the effects of each of these factors on changes in various summary measures of inequality over the period. The results find that changes in household structure (particularly the declining proportion of two-parent families), attributes, and employment outcomes each contribute to the observed increase in inequality, while the changes in returns are estimated to reduce the level of inequality. Collectively these factors account for about 50 percent of the observed increase, depending on the measure of inequalit used. The results confirm other research findings that the changes were concentrated during the late 1980s.
This is a Treasury working paper 2001/21 and is available at www.treasury.govt.nz/workingpapers/2001.


8 August 2001, Brian Pink

Speaker: Brian Pink, Government Statistician, Statistics New Zealand

Title: The Impact of IT on Official Statistics

Time: 5:30pm, Wednesday 8 August 2001 (refreshments from 5pm)

Place: 1st Floor Meeting Room, Science House, Royal Society of NZ, Turnbull St


Last Modified: Friday, 27th November 2015