Transforming SIBTEST to Account for Multilevel Data Structures

SIBTEST is a differential item functioning (DIF) detection method that is accurate and effective with small samples, in the presence of group mean differences, and for assessment of both uniform and nonuniform DIF. The presence of multilevel data with DIF detection has received increased attention. Ignoring such structure can inflate Type I error. This simulation study examines the performance of newly developed multilevel adaptations of SIBTEST in the presence of multilevel data. Data were simulated in a multilevel framework and both uniform and nonuniform DIF were assessed. Study results demonstrated that naive SIBTEST and Crossing SIBTEST, ignoring the multilevel data structure, yield inflated Type I error rates, while certain multilevel extensions provided better error and accuracy control.