Fellas: I would like to comment on all this marginal testing/ multiplicity adjustment/ Fold change/T test stuff.. My comment is: "let's keep our eyes on the prize": the scientific questions about biological systems that can be addressed with array data. In my opinion these REAL and RELEVANT questions are NOT so essentially tied to the marginal testing issues for single genes. In my opinion, the real questions about microarray data ARE NOT single gene questions. Focusing on marginal tests of single genes IS KIND OF A WASTE OF TIME. It the kind of thing that makes statisticians irrelevant to scientific inquiry. The kind of thing that makes us accessories rather than scientists. IT IS A MISUSE of MULTIVARIATE DATA to myopically focus on single gene results. A sin, no less. Don't kid yourself. My comment would be: build evidence for biolgoical phenomena ACROSS THE 10ks of genes on the array. Use bioinformatic knowledge to pin together the evidence. GO FIGURE. Let's be SCIENTISTS. Lets focus on the REAL questions. All the truths about MTA are still true. They have use. FDR is still a good idea. The T distribution is still a pillar. The question is the appropriate scale of biological inquiry at which to do the testing. Single gene hit lists just suck. Quote me. CASHAW