Differential item functioning and ad hoc interpretations

Document Type : Original Article


University of Tehran



A plethora of research studies has focused on Differential Item Functioning. Despite the diversity of DIF detection techniques offered, little research has been done on the interpretation of DIF results. This study was undertaken to investigate whether there is any order to the interpretations offered for the real cause of items flagged as displaying DIF. The analysis of the opinion of experts showed that there is no such order. It is argued that such “ad hoc” interpretations have rendered DIF analysis of little use. It is further suggested that research should focus on devising a mechanism for basing DIF interpretations on principled grounds.