Detection of differential item functioning in the graded response model

Abstract

Methods for detecting differential item functioning (DIF) have been proposed primarily for the item response theory dichotomous response model. Three measures of DIF for the dichotomous response model are extended to include Samejima’s graded response model: two measures based on area differences between item true score functions, and a χ² statistic for comparing differences in item parameters. An illustrative example is presented. Index terms: differential item functioning, graded response model, item response theory.