There has been growing use of ideal point models to develop scales measuring important psychological constructs. For meaningful comparisons across groups, it is important to identify items on such scales that exhibit differential item functioning (DIF). In this study, the authors examined several methods for assessing DIF on polytomous items…

This review employs a conceptual framework that distinguishes methods of detecting measurement bias based on either observed or unobserved conditional invariance models. The primary interest is in group-level measurement bias. Methods for bias detection in both continuous and ordered-categorical measures are reviewed, as are methods for testlets…