To estimate SNP heritability for males and females, we use the equation E[χi2]=1+Nihi2Meff, where i ∈ {m, f} indicates males or females, E[χi2] is the expected χ2 statistic, hi2 is the SNP heritability for the X chromosome, Ni is the GWAS sample size, and Meff is the effective number of SNPs (which is assumed to be the same in males and females). We replaced E[χi2] with its sample analog and Meff with its estimated value, and then we solved for hi2.
