设离散型随机变量X的分布律为P(X=n)=P(X=-n)=1/2n(n+1),1,2,...,求E(X)
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设离散型随机变量X的分布律为P(X=n)=P(X=-n)=1/2n(n+1),1,2,...,求E(X)
设离散型随机变量X的分布律为P(X=n)=P(X=-n)=1/2n(n+1),1,2,...,求E(X)
设离散型随机变量X的分布律为P(X=n)=P(X=-n)=1/2n(n+1),1,2,...,求E(X)
E(x)=∑x*px=∑{[n*1/2n(n+1)]+[-n*1/2n(n+1)]} (n=1,2,...)
=∑[(n-n)*1/2n(n+1)]
=0