设随机变量X与Y相互独立,且X~N(3,1/6),N(2,1/3),则D(X-Y+1)=

Question

设随机变量X与Y相互独立,且X~N(3,1/6),N(2,1/3),则D(X-Y+1)=

Answer 1

D(X-Y+1)=1^2*DX+(-1)^2*DY+1^2*D(1)=DX+DY=1/6+1/3=1/2