Introduction

Methods for detecting differential item functioning (DIF) and item bias typically are used in the process of developing new measures, adapting existing measures, or validating test score inferences. DIF methods allow one to judge whether items (and ultimately the test they constitute) are functioning in the same manner in various groups of examinees. In broad terms, this is a matter of measurement invariance; that is, is the test performing in the same manner for each group of examinees? What follows is a brief introduction to DIF and item bias, including the context in which DIF methods arose. The goal is to provide some organizing principles that allow one to catalogue and then contrast the various DIF detection methods. This entry will end with a discussion ...