f4-statistics can be used to test asymmetries in allele sharing between populations. They measure the covariance between allele-frequency differences across two pairs of populations. Theory and formula An f4-statistic is the average, across SNPs, of the product of the allele-frequency differences between two pairs of populations: f4(A,B;C,D)=Ei[(pA,i−pB,i)(pC,i−pD,i)] f_4(A,B;C,D)=\mathbb{E}_i\left[(p_{A,i}-p_{B,i})(p_{C,i}-p_{D,i})\right] f4(A,B;C,D)=Ei[(pA,i−pB,i)(pC,i−pD,i)]Multiplying out results in: ...
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