• New introductory/overview page on latent structure models for rater agreement and multiple diagnostic tests
• Reprint uploaded: Uebersax JS. Statistical modeling of expert ratings on medical treatment appropriateness Journal of the American Statistical Association, 88, 1993, 421-427. (By permission of JASA) (March 2010)
• Expanded and updated bibliography on Latent Class Models for Rater and Diagnostic Agreement (October 2009)
• Reprint uploaded: Uebersax JS. Modeling approaches for the analysis of observer agreement. Investigative Radiology, 27(9), 1992, 738-743. (By permission of Kluwer Academic Journals) (September 2009)
• Some aspects of Latent Structure Analysis
  
  lecture by Mike Titterington, University of Glasgow (October 2008)
• New page: Latent correlation with skewed latent distributions: a generalization of the polychoric correlation coefficient and a computer program for estimation; updated Tetrachoric and Polychoric Correlation Coefficients; (February 2008)
  
• New online article: Bayesian Unconditional Power Analysis. (July 2007)
  
• New program LTA-2 for latent trait analysis and IRT modeling with dichotomous items. (September 2006)
• Added the Bhapkar marginal homogeneity test to the MH Program (August 2006)
• New page: Factor analysis and SEM with tetrachoric and polychoric correlations (August 2006).
• New software: MVN - Generate random multivariate normal data easily. (July 2006).
• New software: TetMat - Estimates a matrix of tetrachoric correlation coefficients. (June 2006).
• New article: Get the most from Command Prompt (June 2006). Don't throw out those old DOS programs!
• New article: Likert scales: dispelling the confusion (June 2006)
• Some programs re-compiled in f90 (June 2006)

Major site update (October 2001)

New LCA software!
Drs. Jeroen Vermunt and Jay Magidson have released their Latent GOLD software for latent class analysis. The program is superb! A technical breakthrough on several fronts. Visit the Statistical Innovations web site for details. (Summer 2000)

New online articles!
Anyone using latent class models should understand the two potential problems of local maximum solutions and local dependence of manifest variables:

• A Brief Study of Local Maximum Solutions in Latent Class Analysis demonstrates the problem of local maxima, shows their frequency, and describes several useful ways to avoid them using LEM, PANMARK, and Latent GOLD.
• A Practical Guide to Local Dependence in Latent Class Models discusses diagnostics for local dependence and describes three ways to handle the problem, with example LEM command files. (Summer 2000)

I have a new site, the Latent Trait Analysis web pages. It has information on latent trait models, item response theory (IRT) models, and methods for factor analysis of binary data. There's also a separate page that discusses the Tetrachoric and Polychoric Correlation Coefficients . (June 2000)

The Statistical Methods for Rater Agreement web site is now up and running. Information on raw agreement indices, kappa statistics, odds ratio measures, latent class and latent trait models, tetrachoric and polychoric correlations, and other methods for analyzing rater and diagnostic agreement data. (May 2000)

New page, Estimating a Latent Trait Model by Factor Analysis of Tetrachoric Correlations . It explains the method and shows how to apply it with LISREL or SAS. (May 2000)

The paper, "Probit Latent Class Analysis," is now in print (December 1999 issue of Applied Psychological Measurement).

Here is an open letter Latent Class Analysis and Psychiatric Research by me and William Grove. It critiques a series of articles that have used Latent Class Analysis to identify subtypes of psychiatric disorders.  These studies have been good overall, but have had certain, recurring methodological problems.  We wish to encourage researchers to address these problems in future studies. (March 1999)