Differential Item Functioning

One of the key techniques researchers use in measurement is to investigate Differential Item Functioning (DIF). In this chapter, we give examples to help define what DIF is and why it is important to understand. Readers are provided with guidance on how to interpret numerous critical Winsteps tables which help one identify items exhibiting DIF. Particular attention is given to how DIF is related to bias and construct validity. The chapter concludes by guiding readers through the steps they might take if they identify an item with DIF for gender. Steps are presented so measures can be computed while retaining the problematic item. This is done by viewing the item as a different item for males and females. The chapter finishes up with a summary discussion between the two students, Keywords and Phrases, Quick Tips, Data Files, References, and Additional Readings. As in almost all chapters, sample analyses are used to reinforce the chapter topic.