This article illustrates the use of an explanatory item response modeling (EIRM) approach in the context of measuring group differences in science achievement. The distinction between item response models and EIRMs, recently elaborated by De Boeck and Wilson (2004), is presented within the statistical framework of generalized linear mixed models.…

A study examined the effect of topic-specific background knowledge on the general quality and local coherence of student writing. Ninety-seven tenth grade students were assigned two writing tasks on specific topics at two points during a semester. J. Langer's measure of topic-specific knowledge was administered prior to each writing task. Each…