A Graphic Procedure for Studying Differential Item Functioning
Abstract A graphic procedure for studying differential item functioning (DIF) designed to provide diagnostic information for psychometricians and educators is presented. Items from a certifying examination in a subspecialty of internal medicine are used as examples. The procedure provides a “signature” of each test item that may be used in conjunction with a summary statistic to flag items showing DIF. Advantages and limitations of the procedure are noted, as are additional areas for investigation.