大学数学
设X服从参数为2的泊松分布,Y=3X-2,试求cov(X,Y)
cov(X,Y)=E[(X-E(X))(Y-E(Y))]= =E[(X-E(X))(3X-2-E(3X-2))]= =3E[(X-E(X))(X-E(X))]=3D(X) X~π(λ) ==> E(X)=D(X)=λ ==> cov(X,Y)=3*2=6
答:D(XY) =E[(XY)^2]-(E(XY))^2 =E[X^2Y^2]-(E(X)E(Y))^2 =E[X^2]E[Y^2]-(1*3))^2 =[D(X)...详情>>
答:详情>>