The performance of some observed and unobserved conditional invariance techniques for the detection of differential item functioning

The current research investigates the performance of some conditional and unconditional invariance measures of differential item functioning (DIF), namely: the log-linear model, the logistic regression model, the signed and the unsigned area, the SOS1 and the SOS3. A simulation study is used to evaluate their ability to detect uniform as well as nondirectional nonuniform DIF under several test conditions. The factors that were subject to experimental manipulation in the simulation study are the size of the DIF, the ability distribution of the focal and the reference group, the sample size, the proportion of DIF items and the length of the test.