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| f = Gamma[a + b + n1]/(Gamma[a + n2] Gamma[b + n1 - n2]) x^(
a + n1 - 1) (1 - x)^(b + n1 - n2 - 1) /. {a -> 3, b -> 5.67,
n1 -> 15, n2 -> 10}
Integrate[ f, {x, 0, 1}]
Integrate[
PDF[BetaDistribution[a + n2, b + n1 - n2], x] /. {a -> 3, b -> 5.67,
n1 -> 15, n2 -> 10}, {x, 0, 1}]
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积分结果不一致前面的是0.0671263，后面是1.
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| Plot[{f, PDF[BetaDistribution[a + n2, b + n1 - n2], x] /. {a -> 3,
b -> 5.67, n1 -> 15, n2 -> 10}}, {x, 0, 1}, PlotRange -> All]
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绘图结果也不一致
f画出来的峰值明显低于用PDF加BetaDistribution的峰值。