From Data to Paper [via Stata!] Tim Croudace and Jon Heron ^ Jon works in Bristol too ;-) ESRC Funded Researcher Development Initiative Project Grant: Course 2: From Data to Paper (via Stata)

From Data to Paper [via Stata!] Tim Croudace and Jon Heron ^ Jon works in Bristol too ;-) ESRC Funded Researcher Development Initiative APPLIED PSYCHOMETRICS Project Grant Course 2: From Data to Paper (via Stata)

Tim Croudace Department of Psychiatry 1- Senior Lecturer (Psychometric Epidemiology) 2- Dept of Health Career Scientist (Public Health) 3- Director of Research: The Psychometrics Centre, Cambridge Newnham College, May 2008 From Data to Paper (via Stata) The origins and genesis of (new) psychometric publications (for you) …

From Data to Paper [via Stata!]

What’s new in psychometrics (1) –Locally- quite a lot! Places New project educational & training project –recently underway Helping more people understand the potential for, and how to do psychometric analyses (better than they currently do) ESRC Researcher Development Initiative (RDI) Project Grant “Applied Psychometrics” [with Prof’s Susan Golombok & John Rust]

What’s new in psychometrics (2) The frontiers of modern multivariate analysis have moved quite a long way … don’t get left behind There are many new procedures in modern statistical computing environments that can improve your research –e.g. the recent explosion of new psychometric routines for quantitative modellers in modern statistical computing packages such as Mplus, Splus, R and Stata see. Journal of Statistical Software, Special Volume: Psychometrics in R See The Stata Journal, or check out what’s new in SAS! In the same way that regression has moved into multilevel, so has factor analysis, structural equation modelling and IRT* –Many of these innovations are due to the power and flexibility of ML estimation –Old favourites are still available and still very useful, just more powerful once extended e.g. Latent class analysis standard model still available but extended to include random effects now applicable to mixed measurement level outcomes and adapted for longitudinal (panel data) and multilevel settings (family data)

From Data to Paper [via Stata!]

Introduction to data preparation considerations/advice for psychometric scaling / psychometric statistical analyses Demonstration (not practicals) of main commands –in Stata for convenience (to us) Helping you to structure your data-based analytical activities before writing up papers Parallel Development of Course Website –Logfile of all demonstrations run during the course –Linkage to example publications –Linkage to websites for other software(s)

From Data to Paper [via Stata!] Introduction to data preparation considerations for psychometric analyses –Data collection Data entry –Data validation Data transformation and recoding Data description and representation Data display and (uni-)dimensionality Psychometric statistics and scaling models Simple/Summary, Non-parametric, Parametric

Data … –Data collection »How you do it is down to you, depends on what you are doing Data entry –Once again down to you, or someone else, unless you beg and borrow all your data from ongoing studies (like Jon and I do! – not true actually :-) ) –Data validation Very important – only allowable responses should be analyses, control over labelling and missing values very important too Most second hand datasets given to me contain >=1 error

Data … Transformation and Recoding –GNIROCS: Reverse scoring (geddit?!) When and Why [Question answer combinations] –Alternate scoring methods / variable recoding –Categorical variable collapsing e.g binary recoding Data description and representation –Summary statistics, distributions, displays Data dimensionality and display –Eigen values, PCA – Factor – Polychoric PCA

Some Sage advice 3 books Scaling Procedures: Issues and Applications –R.G. Netemeyer, W.O. Bearden and S. Sharma Fundamentals of Item Response Theory (IRT) –R.K. Hambleton, H. Swaminathan and H.J. Rogers Introduction to Nonparametric IRT – Mokken Scaling –K. Sijtsma and I.W. Molenaar Test Theory: A unified approach –R.P. McDonald. »Comprehensive Psychometric Overview –Linear Factor Analysis –Categorical Data »(Binary Factor Analysis=Item Response Theory) –Both understood through the Common Factor Model

Recommended books on general multivariate analysis –The Analysis and Interpretation of Multivariate Data for Social Scientists [AIMDSS] David.J. Bartholomew et al. [LSE teaching team] –2 nd edition due out this/next month –Multivariate analysis techniques in social science research: [“From Problem to Data”] Jacques Tacq

What we have in common? - multivariate data

GENESIS study – composite index “a dimensional phenotype”

Data of mixed measurement level: binary/ordinal