This study compared three procedures-the Mantel-Haenszel (MH), the sim
ultaneous item bias (SIB), and the logistic regression (LR) procedures
-with respect to their Type I error rates and power to detect nonunifo
rm differential item functioning (DIF). Data were simulated to reflect
a variety of conditions: The factors manipulated included sample size
, ability distribution differences between the focal and the reference
groups, proportion of DIF items in the test, DIF effect sizes, and ty
pe of item. 384 conditions were studied. Both the SIB and LR procedure
s were equally powerful in detecting nonuniform DIF under most conditi
ons. The MH procedure was not very effective in identifying nonuniform
DIF items that had disordinal interactions. The Type I error rates we
re within the expected limits for the MH procedure and were higher tha
n expected for the SIB and LR procedures; the SIB results showed an ov
erall increase of approximately 1% over the results.