Identifying Possible Sources of Differential Functioning Using Differential Bundle Functioning with Polytomously Scored Data

Oshima, Raju, Flowers, and Slinde (1998) described procedures for identifying sources of differential functioning for dichotomous data using differential bundle functioning (DBF) derived from the differential functioning of items and test (DFIT) framework (Raju, van der Linden, & Fleer, 1995). The purpose of this study was to extend the procedures for dichotomous DBF to the polytomous case and to illustrate how DBF analysis can be conducted with polytomous scoring, common to psychological and educational rating scales. The data set used was parent and teacher ratings of child problem behaviors. Three group contrasts (teacher vs. parent, boy vs. girl, and random groups) and two bundle organizing principles (subscale designation and random selection) were used for the DBF analysis. Interpretations of bundle indexes in the context of child problem behaviors were presented.