设随机变量ξ 满足Eξ=-1,Dξ=3,则E[3(ξ 2-2)]=( )
A. 9
B. 6
C. 30
D. 36
人气:312 ℃ 时间:2020-01-27 22:14:56
解答
∵Dξ=E(ξ2)-[E(ξ)]2,Eξ=-1,Dξ=3,
∴E(ξ2)=3+(-1)2 =4.
再由性质:E(kξ)=kE(ξ),E(X+Y)=E(X)+E(Y)
得E[3(ξ 2-2)]=3E[(ξ2-2)]=3[E(ξ2)+E(-2)]=3(4-2)=6
故选B.
推荐
- 设随机变量X的分布函数F(x)在x
- 对任意随机变量X,若E(X)存在,则E(E(E(X)))等于( ).
- 设随机变量X~N(1,4),则E(X的2平方)等于多少?
- 设随机变量x~N(μ,σ^2)则E(x)=3,D(x)=1,则P(-1
- 设离散型随机变量ξ满足Eξ=3,Dξ=1,则E[3(ξ-1)]等于( ) A.27 B.24 C.9 D.6
- To suggest that the student did not do the reading
- -lg5 -lg7 怎么化成1\5 1\7
- at ease,be likely to,in general,lose face,defend aganist,turn one's back to用五句话编一个故事
猜你喜欢