USING DIF DISSECTION METHOD TO ASSESS EFFECTS OF ITEM DELETION
Yanling Zhang, Neil J. Dorans, Joy L. Matthews-López · ETS Research Report Series · 2005
Statistical procedures for detecting differential item functioning (DIF) are often used as an initial step to screen items for construct irrelevant variance. This research applies a DIF dissection method and a two-way classification scheme to SAT Reasoning Test™ verbal section data and explores the effects of deleting sizable DIF items on reported scores after re-equating. The DIF dissection approach and the two-way classification scheme may yield new and detailed insight into item functioning at the subgroup level. Two hypotheses are studied: (1) whether or not the deletion of a sizeable DIF item that is the most disadvantageous to a particular subgroup will affect the scores for that subgroup the most; and (2) whether or not the effects of item deletion on scores can be predicted by the standardization method. Both hypotheses are supported by the results of this research.