Hi !

I am confused with how to calculate Cronbach's alpha of IAT ,
and I think that the calculation of Cronbach's alpha of IAT and ST-IAT will be the same ,right?

 It will be kind of you if you can tell me how to resolve this problem.

Thank you very much!

If you want to calculate Cronbach's alpha, you essentially
- compute difference scores for every single trial of the combined blocks,
- treat those as separate items, and
- calculate alpha over that.

I'll note that the more common (and easier) approach to assess IAT reliability is some variation of split-half reliability, e.g. calculation the correlation between the D-score for the 1st combined blocks (da) and the D-score for the 2nd combined blocks (db). https://faculty.washington.edu/agg/pdf/Schnabel%20&%20al.Hbk_2008.proofs.pdf gives a short overview of the various approaches.