Unrepeatable Repeatabilities: A Common Mistake

Repeatability is a useful tool for the population geneticist or genetical ecologist, but several papers have carried errors in its calculation. We outline the correct calculation of repeatability, point out the common mistake, show how the incorrectly calculated value relates to repeatability, and provide a method for checking published values and calculating approximate repeatability values from the F ratio (mean squares among groups/ mean squares within groups).