Sample invariance of the structural equation model and the item response model: A case study

Abstract

The sample invariance of item discrimination statistics is evaluated in this case study using real data. The hypothesized superiority of the item response model (IRM) is tested against structural equation modeling (SEM) for responses to the Center for Epidemiologic Studies-Depression (CES-D) scale. Responses from 10 random samples of 500 people were drawn from a base sample of 6,621 participants across gender, age, and different health groups. Hierarchical tests of multiple- group structural equation models indicated statistically significant differences exist in item regressions across contrast groups. Although the IRM item discrimination estimates were most stable in all conditions of this case study, additional research on the precision of individual scores and possible item bias is required to support the validity of either model for scoring the CES-D. The SEM approach to examining between-group differences holds promise for any field where heterogeneous populations are assessed and important consequences arise from score interpretations. © 2003, Lawrence Erlbaum Associates, Inc.