Given an urn with N genes, ugh - I mean with N balls, B of which are white, I can calculate the probability of randomly drawing b or more white balls in a sample of n using hypergeometric test. This gives me a p-value I can use to reject H0.
However, I'd like to use an estimate of the effect size. I use (b/n)/(B/N) ("relative enrichment") but it seems sometimes to be very misleading. Is there a better option?