Hi Mike,

how can I explain in terms of raw data what it means a contrast of 0.5 logits or another one of -0.70 logits after the DIF analysis?

Thanks,
Ani

Ani, if you are looking at Winsteps output, then the DIF sizes are also shown as the "Obs-Exp Average" difference in the observations for this sample of persons. http://www.winsteps.com/winman/index.htm?table30_1.htm

Generally, compute the expected score by a person at the mean ability of the sample for (mean ability - item difficulty + half the contrast) - (mean ability - item difficulty - half the contrast) using a logit-to-expected-score table such as http://www.winsteps.com/winman/index.htm?whatisalogit.htm