負の超幾何分布の確率分布は \[\Pr[x;W,B,b]=\frac{\left(\begin{array}{c}x+b-1\\x\end{array}\right)\left(\begin{array}{c}W+B-b-x\\W-x\end{array}\right)}{\left(\begin{array}{c}W+B\\W\end{array}\right)}\]
-- しましま