Dear list, A collaborator has asked if it is possible to calculate a general power value of the experiment once it has been done. I believe power is set prior to designing the experiment, as the same time as defining significance level, so that the sample size can be estimated. I think I can calculate the power for individual genes that have come out as d.e. using their group means and SD, the number of samples available and the significance value, but I am not sure this is actually useful but is it possible to calculate a, say, "general experimental power value" given the number of replicates per condition is already set? Hope I make myself understandable. Thanks in advance, David