设随机变量X~B(3,0.4),且随机变量Y=(3-X)/2,则E(Y)= 设随机变量x~b(4,1/2),则e(x^2+1)=
\u8bbe\u968f\u673a\u53d8\u91cfX\uff5eb(3,0.4),\u4e14\u968f\u673a\u53d8\u91cfY=X\uff083-X\uff09/2\uff0c\u5219p{X=Y}=\u627e\u51fa\u80fd\u6ee1\u8db3\u6761\u4ef6\u7684X\u53d6\u503c\u5373\u53ef\u6c42\u51fa\u6982\u7387\uff0c\u8fc7\u7a0b\u5982\u56fe\u3002\u7ecf\u6d4e\u6570\u5b66\u56e2\u961f\u5e2e\u4f60\u89e3\u7b54\uff0c\u8bf7\u53ca\u65f6\u91c7\u7eb3\u3002\u8c22\u8c22\uff01
E(X)=3×0.4=1.2
E(Y)=3/2-1/2·E(X)=1.5-0.6=0.9
【附注】
(1)X~B(n,p),则 E(X)=np
(2)E(kX+b)=kE(X)+b
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