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Re:那就给个简单推导吧

Posted by mikezheng0 at 2008-09-06 22:13:12 on Problem 3682
In Reply To:那就给个简单推导吧 Posted by:Cpp at 2008-09-01 00:09:05 
> 将巴斯卡分布看做k个二项分布
> 二项分布E(X)=1/p; D(X)=(1-p)/p^2
> 巴斯卡分布E(X)=k/p; D(X)=k(1-p)/p^2
> 又因为D(X)=E(X^2)-E(X)^2
> 题目求巴斯卡的E(X)和E(X^2)=D(X)-E(X)^2 
E(X)=1/p; D(X)=(1-p)/p^2不是二项分布，应该是几何分布！
二项分布E(X)=np; D(X)=np(1-p)
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