We previously named the SNP-based method mentioned GREML [11], as a complement to GBLUP [12] where variance components are assumed known, and have been implemented them in the software tool GCTA [13]. One outstanding question is the statistical power of detecting genetic variation using the population-based estimation method, for example how many samples are required to achieve estimates that are sufficiently accurate to detect genetic (co)variance of complex traits. In this paper, we derive the sampling variance of the estimate of genetic (co)variance by analytical derivations and verify our derivations by simulations under a range of scenarios. We also provide an online tool for power calculation.
