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Beta Binomial Conjugacy

Prior h(ฯƒ)โˆผBeta(ฮฑ,ฮฒ)h(\sigma) \sim \text{Beta}(\alpha, \beta)

Likelihood g(xโˆฃฮธ)โˆผBinomial(n,x,ฮธ)g(x|\theta) \sim \text{Binomial}(n, x, \theta)

Posterior

f(ฮธโˆฃx)=g(xโˆฃฮธ)h(ฮธ)โˆซฮธg(xโˆฃฮธ)h(ฮธ)dฮธf(\theta | x) = {{g(x | \theta) h(\theta)} \over {\int\limits_{\theta} g(x|\theta) h(\theta) d \theta}}

โˆดf(ฮธโˆฃx)โˆผBeta(ฮฑ+x,ย ฮฒ+nโˆ’x)\therefore f(\theta | x) \sim \text{Beta}(\alpha + x,~\beta + n - x)