如果随机变量X和Y满足D(X+Y)=D(X-Y),则下列各结论正确的是_____A D(Y) =0 B D(X)D(Y) =0 C X和Y相互独立D X和Y不相关

4、若随机变量X,Y满足 (X+Y)=D(X-Y), 则下列式子正确的是 ()-|||-(A)X与Y相互独立 (B) D(X)D(Y)=0-|||-(C)X与Y

设随机变量X,Y的期望和方差存在，且D(X-Y)=D(X)+D(Y)，则下列说法不正确的是（ ）A D(X+Y)=D(X)+D(Y)B E(XY)=E(X)E

如果随机变量X与Y,满足D(X+Y)=D(X-Y),则必有（ ）如果随机变量X与Y,满足D(X+Y)=D(X-Y),则必有（）A.D(Y)=0B.存在a，b使

设X与Y为随机变量,则与 Cov(X,Y)=0 不等价的是 () .-|||-(A)X与Y一定独立; (B)X与Y一定不相关;-|||-(C) D(X+Y)=D

设随机变量(X,Y)满足方差D(X+Y)=D(X-Y),则必有A. X与Y独立B. X与Y不相关C. X与Y不独立D. (X)=0或D(Y)=0

设X和Y为两个随机变量，已知E(XY)=E(X)E(Y)，则必有（）A D(XY)=D(X)·D(Y)B D(X+Y)=D(X)+D(Y)C X和Y相互独立D

对两个随机变量X与Y，若 E(XY)=E(X)E(Y)，则A D(X+Y)=D(X)+D(Y)B X 与 Y 相互独立C X 与 Y 不相互独立D D(XY)=

若随机变量X与Y满足 D(X+Y)=D(X)+D(Y), 则( )。A. x与Y相互独立B. x与Y不相关C. x与Y不独立D. x与Y不独立,也不相关

4.设随机变量(X,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. X与Y不相互独立D. D(X)=0或D(Y)=0

设X,Y为随机变量，且E(XY)=E(X)E(Y),则有( )。A.D(XY)=D(X)D(Y) B.D(X+Y)=D(X)+D(Y)C.X,Y相互