Latent Class Analysis of Differential Item Functioning on the Peabody Picture Vocabulary Test–III

Abstract

This study investigated the use of latent class analysis for the detection of differences in item functioning on the Peabody Picture Vocabulary Test—Third Edition (PPVT-III). A two-class solution for a latent class model appeared to be defined in part by ability because Class 1 was lower in ability than Class 2 on both the PPVT-III and the Expressive Vocabulary Test (EVT). This difference was much larger on the PPVT-III for the low-ability class. No difference was found for the high-ability latent class, suggesting that the difference was a result of something in the PPVT-III that was not present in the EVT. The difference on the PPVT-III for low-ability children appeared to be a result of the structure of the items on the test, which seems to encourage the overriding use of the novel name—nameless category strategy for the selection of an answer—a strategy not available on the EVT.