The comparison of differential item functioning predicted through experts and statistical techniques

Abstract

Validity is one of the psychometric properties of the achievement tests. To determine the validity, one of the examinations is item bias studies, which are based on Differential Item Functioning (DIF) analyses and field experts’ opinion. In this study, field experts were asked to estimate the DIF levels of the items to compare the estimations obtained from different statistical techniques. Firstly, the experts were asked to examine the questions and make the DIF level estimations according to the gender variable for the DIF estimation, and the agreement of the experts was examined. Secondly, DIF levels were calculated by using logistic regression and the Mantel-Haenszel (MH) statistical method. Thirdly, the experts’ estimations and the statistical analysis results were compared. As a conclusion, it was observed that the experts and the statistical techniques were in agreement among themselves, and they were partially different from each other for the Sciences test and equal for the Social Sciences test.

Keywords: Item bias, differential item functioning (DIF), expert estimation.