Generalized Discriminant Analysis: Some Illustrations

The versatility of discriminant analysis as a technique to obtain more parsimonious descriptions in multivariate studies has not been fully exploited. Although the technique has been commonly proposed and used for multivariate analysis of variance studies, there have been few applications for other models and effects of current interest in the behavioral sciences. This article briefly reviews generalized discriminant analysis as a descriptive technique associated with the multivariate general linear model, and then presents results for several example analyses. The examples, based on real data, include contextual effects analyses using multilevel models and an aptitude-treatment-interaction analysis. It is argued that discriminant analysis has the most value as a descriptive technique when used in the spirit of an "external factor analysis."