An item response theory-based statistical procedure for detecting concurrent internal bias in ability tests

A statistical procedure is developed with the purpose of detecting internal bias occurring concurrently in several items in an ability test. Concurrent internal bias (CIB) is considered in a nonparametric multidimensional item response theory (IRT) model which models both an ability intended to be measured by the test (target ability) and nuisance determinant abilities. If the nuisance ability distributions conditional on a fixed target ability are different across group, and contamination of several items with these nuisance abilities is present in their item response functions, then bias occurs concurrently in these items.