Identifying Differential Item Functioning of Rating Scale Items With the Rasch Model: An Introduction and an Application

Abstract

This study (a) provided a conceptual introduction to differential item functioning (DIF), (b) introduced the multifaceted Rasch rating scale model (MRSM) and an associated statistical procedure for identifying DIF in rating scale items, and (c) applied this procedure to previously collected data from American coaches who responded to the coaching efficacy scale (CES; Feltz, Chase, Moritz, & Sullivan, 1999). In this study, an item displayed DIF if coaches from different groups were more or less likely to endorse that item once coaches were matched on the efficacy of interest, where Motivation, Game Strategy, Technique, and Character Building efficacies defined coaching efficacy. Coach gender and level coached were selected as the grouping variables. None of the Technique and Character Building items exhibited DIF based on coach gender or level coached. One of the Motivation items and one of the Game Strategy items exhibited DIF based on coach gender. Two of the Motivation items exhibited DIF based on level coached.