I'm not going to provide all of the gory details on the Bayesian model. If you're interested you can find most of them in my lecture notes from the Summer Institute in Statistical Genetics last summer.2 In fact, I'm only going to describe two pieces of the model.3 First, a little notation:


To complete the Bayesian model, all we need are some appropriate
priors. Specifically, we so far haven't done anything to describe the
variation in allele frequency among populations. Suppose that the
distribution of allele frequencies among populations is
well-approximated by a Beta distribution. A Beta
distribution is convenient for many reasons, and it is quite
flexible. Don't worry about what the formula for a Beta distribution
looks like. All you need to know is that it has two parameters and
that if these parameters are
and
, we can set things up
so that

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