设(X,Y)为二维随机向量,E(X)=E(Y)=0,D(X)=16,D(Y)=25,=0.6,则有Cov(X,Y)=
问题描述:
设(X,Y)为二维随机向量,E(X)=E(Y)=0,D(X)=16,D(Y)=25,=0.6,则有Cov(X,Y)=
答
由 ρ = Cov(X,Y)/[D(X)D(Y)]^0.5
Cov(X,Y) = ρ[D(X)D(Y)]^0.5
= 0.6X4X5
= 12