设=4, =1, rho xy=0.5，则=4, =1, rho xy=0.5( ) A.=4, =1, rho xy=0.5B.=4, =1, rho xy=0.5C.=4, =1, rho xy=0.5D.=4, =1, rho xy=0.5

已知随机 变量 X 与 Y 的相关系数(rho )_(xy)=0.5，且(rho )_(xy)=0.5__________.已知随机变量X与Y的相关系数，且__

9.设 (X)=E(Y)=2, D(X)=1 (Y)=4, 且 rho xy=0.5, 则 |X-Y|geqslant 6 -|||-≤ __ .

设D(X)=25 D(Y)=16 (rho )_(xy)=0.4,则D(X)=25 D(Y)=16 (rho )_(xy)=0.4,D(X)=25 D(Y)=1

若D(X) =4,D(Y) =9, rho xY=0.5,Z=2 X-3 Y+5,则D(Z) =_______.若D(X)=4,D(Y)=9,,Z=2X-3Y+

6、设 D(X)=4 ,D(Y)=9 ,(rho )_(xy)=0.25 则 (5x-y+15)= __

18.设随机变量X,Y满足 E(X)=1 D(X)=1 E(Y)=2 D(Y)=4 ,(rho )_(xy)=0.5 ,-|||-令 =dfrac (X)(2)

设有随机变量X，Y，Z,已知EX=1, EY=2,EZ=-1,DX=1,DY=2,DZ=3,且rho xY=0,, rho xz=dfrac (1)(2), r

已知D(X)=4，D(Y)=1，rho xy=0.6，求D(X+Y)，D(3X-2Y)已知D(X)=4，D(Y)=1，，求D(X+Y)，D(3X-2Y)

设backsim N(1,(3)^2) backsim N(0,(4)^2) 且X与Y的根关-|||-系数 (rho )_(xy)=-1/2, 则 Cov(X,

设随机变量X~N(0,1),Y~N(1,4),且 rho_(XY)=-(1)/(2),设 Z=(1)/(3)X+(1)/(2)Y,则D(Z)=（）A. 7/9B