Module 28: Raju’s Differential Functioning of Items and Tests
Nambury S. Raju (1937–2005) developed two model-based indices for differential item functioning(DIF) during his prolific career in psychometrics. Both methods, Raju’s area measures (Raju, 1988) and Raju’s DFIT (Raju, van der Linden, & Fleer, 1995), are based on quantifying the gap between item characteristic functions (ICFs). This approach provides an intuitive and flexible methodologyfor assessing DIF. The purpose of this tutorial is to explain DFIT and show how this methodology can be utilized in a variety of DIF applications.
Keywords: differential item functioning, DIF, differential test functioning, DTF, item response theory, IRT, measurement equivalence, Raju