full size reduces statistical power to detect significance, particularly when effects are small (as most SNP effects are). For example, a regression with a main effect powered at 80 % (the accepted minimum level) has only 29 % power to detect an interaction effect of the same size (Brookes et al. 2004). When adjustments are made for multiple testing, statistical power is reduced even further, making it very difficult to detect and replicate significant gender-genotype interactions.
