Confucius pointed out that the first step toward wisdom is calling things by the right name. The term "Differential Item Functioning" (DIF) did not arise fully formed from the miasma of psychometrics, it evolved from a variety of less accurate terms. Among its forebears was "item bias" but that term has a pejorative connotation…

Although differential item functioning (DIF) theory traditionally focuses on the behavior of individual items in two (or a few) specific groups, in educational measurement contexts, it is often plausible to regard the set of items as a random sample from a broader category. This article presents logistic mixed models that can be used to model…