Log-Linear Models for Change in Manifest Categorical Variables

Abstract

Applied developmental scientists engaged in the evaluation of community-based programs, in tests of therapeutic effectiveness, or in developmental research on special populations (e.g., youth gang members, street children, or refugees) must often conduct individual or contextual analyses that involve multiple categorizations over time. This article discusses models for analysis of change in cross classifications of nominal or ordinal variables. Examples of such models include Clogg, Eliason, and Grego's (1990) change-persistence models and quasi-independence models for nominal or ordinal variables. A definition of trends in nominal level variables is provided. A general model is specified, and two groups of log-linear models are presented as special cases of this model. The first allows researchers to test specific hypotheses concerning, for example, general trends and trends in subtables. The second group extends application of log-linear modeling of mobility tables to rectangular tables. Examples use data from research on change in schizophrenics and from pubertal development.