Dear BioC, I've been using a weighted Stouffer method to combing p-values (one- tailed) derived from multiple microarray experiments performed in independent labs. Each experiment roughly address the same null hypothesis: addition of receptor ligand for 24h has no effect on gene expression. I have then taken the combined Stouffer z-score and transformed it back to a two-tailed p-value followed by FDR correction to address Type 1 errors. I would now like to address the likely magnitude of Type 2 errors. Unfortunately I'm not in a position to do any wet bench experiments to validate a randomly selected subset of the data points. I would be grateful if someone could direct me to a suitable correction or method which might help to get a handle on the type 2 error involved when doing thousands of weighted Stouffer calculations. Scott A. Ochsner, Ph.D. NURSA Bioinformatics Molecular and Cellular Biology Baylor College of Medicine Houston, TX. 77030 phone: 713-798-6227