Chatomics Field GuideWhat They Don't Teach You

Topic

Multiple testing and FDR

Why do I have zero significant genes after adjustment, and is that correct?

Testing 20,000 genes at p < 0.05 gives 1,000 false positives by construction. Benjamini-Hochberg controls the false discovery rate but is sensitive to how many tests you ran, which is why independent filtering and pre-filtering of low-count genes change your result list.