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), rho yz=-dfrac (1)(2),分别求D(X+Y+Z)和rho xY=0,, rho xz=dfrac (1)(2), rho yz=-dfrac (1)(2),

26.设X,Y,Z为三个随机变量,且 (X)=E(Y)=1, E(Z)=-1 (X)=-|||-D(Y)=DZ=1 (rho )_(x)y=0, (rho )_

2.已知随机变量X Y分别服从N(1,4^2 ),N(0,3^2),它们的相关系数 (rho )_(xy)=-dfrac (1)(2), 设 =-|||-dfr

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

设随机变量 (X,Y)sim N(0,0,1,4,rho ), (2X-Y)=1, 则 rho = __

4.设随机变量 sim N(1,9) , sim N(0,16) ,相关系数 (rho )_(xy)=-dfrac (1)(2) ,设-|||-.=dfrac

17.设随机变量X与Y相互独立，且EX=2，DX=1，EY=1，DY=4，求U=X-2Y与V=2X-Y的相关系数rho_(UV)。17.设随机变量X与Y相互独立

3.设 approx N(0,(4)^2), approx N(1,(3)^2), 且 (rho )_(x)=-dfrac (1)(2), 令 =dfrac (

已知 approx N(1,(3)^2), backsim N((0.4)^2), 且X与Y的相关系数 rho =-1/2, 设 =dfrac (x)(3)--

1.(1)设随机变量X满足: EX=11 =9, 试用切比雪夫不等式估计 (2lt Xlt 20);-|||-(2)设随机变量X,Y满足: =EY=0, =4,