Differential Item Functioning (DIF): Current problems and future directions

With the rising concerns over the fairness of language tests, Differential Item Functioning (DIF) has been increasingly applied in bias analysis. Despite it widespread use in psychometric circles, however, DIF is facing a number of serious problems. This paper is an attempt to shed some light on a number of the issues involved in DIF analysis. Specifically, the paper is focused on four problems: the inter-method indeterminacy, the intra-method indeterminacy, the ad hoc interpretations, and the impact of DIF on validity. In order to orient the reader, the paper also provides a brief introduction the fundamental concepts in DIF analysis.