Power Formulas for Lord's Wald Test for Uniform and Non-Uniform Differential Item Functioning

• In Event: Poster Session 15
  In Poster Session: Accuracy and Meaning in Modeling

Abstract

In this paper we derive a power formula of the Lord’s Wald test for the differential item functioning (DIF). Lord’s Wald test is a popular method for detecting uniform and non-uniform differential item functioning (DIF) effects based on IRT model. As shown in the derived formula, the asymptotic power is related to the sample size, effect size of DIF, the item response function (IRF) and the distribution of the latent trait of the reference and the focal groups. A Monte Carlo simulation study shows that the theoretical values calculated from the formulas derived in the paper are close to what are observed in the simulated data.

Author

• Zhushan Mandy Li, Boston College