A . I=J
B . I=2J
C . I=3J
D . I=4J
[单选题]已知D(X)=1,D(Y)=16,ρXY=0.5,则D(X+Y)=( )A.18B.19C.21D.17
[单选题]已知D(X)=2,D(Y)=3,则Cov(X+Y,X-Y)等于().A . 1B . -1C . 5D . 6
[单选题]如果X与Y满足D(X+Y)=D(X-Y),则必有()。A.X与Y相互独立B.X与Y不相关C.D(Y)=0D.D(X)·D(Y)=0
[单选题]已知D(X)=4,D(Y)=9,Cov(X+Y)=2,则D(3X-2Y)等于().A . 96B . 72C . 48D . 36
[问答题]D(X)=4,D(Y)=9,ρXY=0.5,则D(X-Y)=----------,D(X+Y)=------------.
[问答题]D(X)=4,D(Y)=9,ρXY=0.5,则D(X-Y)=-------------,D(X+Y)=-------------.
[问答题]已知D(X)=25,D(Y)=36,X与Y的相关系数ρXY=0.4,则D(X+Y)=().
[单选题]设(x-y)(x+2+y)-15=0,则x+y的值是()。A.-5或3B.-3或5C.3D.5
[单选题]D域由x轴,x2+y2-2x=0(y≥0)及x+y=2所围成,f(x,y)是连续函数,转化为二次积分为()。A . B . C . D .
[问答题]若X~N(O,1),Y~N(O,2)且X与Y独壶,则X+Y~().