of population structure, there is no loss in power compared to a test that does not correct for axes of genetic variation. Furthermore, there is a substantial increase in power over studies that do not make use of external reference samples as controls. This approach has broad applicability to GWA studies, making use of the increasing number of raw genotype data sets which are being made publicly available to increase the power to detect novel disease loci, whilst remaining computationally tractable and rigorous to population structure.
