Basics of Differential Item Functioning
Stefanie A. Wind, Hua Cheng · 2022
This chapter provides a basic overview of differential item functioning (DIF) along with methods for detecting DIF with Rasch models using R. DIF occurs when examinees who are members of different groups who have the same location on the latent variable have different probabilities for a response in a given category on an item. The interpretation and use of DIF indices varies along with the individual purpose and consequences of each assessment. The chapter demonstrates two techniques that analysts can use to identify DIF within the Rasch measurement theory framework. A popular method for identifying DIF within the framework of Rasch measurement theory is to calculate group-specific estimates of item difficulty, and compare those estimates to see if they are meaningfully different.