study the predictive accuracy of scores estimated from finite case/control studies, but did not obtain an explicit relation between sample size and accuracy. Similarly, the International Schizophrenia Consortium (ISC) [3] used simulations to show empirical relations between sample size and accuracy under several genetic models. Daetwyler et al [23] considered the effect of sampling variation on the correlation between polygenic score and total genetic value. Their results can be adapted to prediction of phenotypes rather than genetic values, and also to other measures of power and accuracy, but their conclusions are limited by an assumption that all the markers have effects and are included in the score.
