Performances Based on Ability Estimation of the Methods of Detecting Differential Item Functioning: A Simulation Study

Abstract

The aim of the study is to examine differential item functioning (DIF) detection methods-the simultaneous item bias test (SIBTEST), Item Response Theory likelihood ratio (IRT-LR), Lord chi square (chi 2), and Raju area measures-based on ability estimates when purifying items with DIF from the test, considering conditions of ratio of the items with DIF, effect size of DIF, and type of DIF. This study is a simulation study and 50 replications were conducted for each condition. In order to compare DIF detection methods, error (RMSD) and coefficient of concordance (Pearson's correlation coefficient) were calculated according to estimated and initial abilities for the reference group. As a result of the study, the lowest error and the highest concordance were seen in the case of 10% uniform DIF in the test and the method of IRT-LR, considering all other conditions. Moreover, for the method of SIBTEST and IRT-LR in all conditions, it was found that the error obtained by purifying items with C level DIF is lower than the error obtained by purifying items with both B and C level DIF. Similarly, for the method of SIBTEST and IRT-LR in all conditions, it was seen that the concordance coefficient found by purifying C level DIF is higher than the coefficient by purifying items with both B and C level DIF.