IMPROVING THE MATCHING FOR DIF ANALYSIS BY CONDITIONING ON BOTH TEST SCORE AND AN EDUCATIONAL-BACKGROUND VARIABLE

When tests are designed to measure dimensionally complex material, DIF analysis with matching based on the total test score may be inappropr iate. Previous research has demonstrated that matching can be improved by using multiple internal or both internal and external measures to more completely account for the latent ability space. The present arti cle extends this line of research by examining the potential to improv e matching by conditioning simultaneously on rest score and a categori cal variable representing the educational background of the examinees. The responses of male and female examinees from a test of medical com petence were analyzed using a logistic regression procedure. Results s how a substantial reduction in the number of items identified as displ aying significant DIF when conditioning is based on total test score a nd a variable representing educational background as opposed to total test score only.