Assessment of differential item functioning in personnel selection

A psychological test should be developed to accurately estimate the measured construct, being insensitive to extraneous factors that could affect it. The way in which the various external factors jeopardize the item responses is known as test bias and minimizing these influences is a primary concern for test developers. A relatively recent category of psychometric techniques that aim to identify those items that function differently in a group of test-takers is called Differential Item Functioning (DIF). The purpose of this paper is to present, in a non-technical manner, the conceptual foundation of DIF, and the most common applied techniques. We will discuss methods based on logistic regression, those using Item Response Theory models as well as the Mantel-Haenszel method. We will then discuss the strengths and limitations of each method, conditions of application, and the main software packages used to conduct such analyses.