1 in 20, or .05. This is what a Bonferroni correction of 5×10−8 does. A popular alternative to a Bonferroni correction is false discovery rate correction, which typically provides less stringent control of Type I errors in favor of controlling the expected proportion of Type I errors under a null and alternative distribution. We do not recommend using the false discovery rate in GWAS. Controlling the family-wise error rate instead allows for greater certainty in our findings before expensive functional follow-up experiments are conducted.
