


设X与Y相互独立,且 sim N(0,1) sim (x)^2(5),-|||-则=dfrac (X)(sqrt {Y/4)}
设X_i sim N(0, 4), i=1, 2, 3, 且相互独立, 则 ()成立。A. $\frac{X_1}{4} \sim N(0,1)$B. $\fr
4.样本X1,X2,···Xn来自总体 sim N(0,1) , overline (X)=dfrac (1)(n)sum _(i=1)^n(X)_(i) ,
4.设相互独立的X和Y具有同一分布,且 sim N(0,dfrac (1)(2)), 则 =X-Ysim underline (N(0,1))
设随机变量 sim N(0,1) sim N(1,1), 且X与Y相互独立,则下列结论中正确的-|||-是 () .-|||-(A) X+Yleqslant
设随机变量sim N(0,1),sim N(0,1),且X与Y相互独立,则sim N(0,1).A.sim N(0,1)B.sim N(0,1)C.sim N(
设 X sim N(0,1), Y sim x^2(n),且 X, Y 相互独立,则 (X)/(sqrt(Y)) sqrt(n) ~A. $t(n)$B. $t
5、随机变量X1,X 2,L,Xn独立且都服从N(2,4)分布,则 overline (X)=dfrac (1)(n)sum _(i=1)^n(X)_(i) 服
若_(i)sim N(0,1), =1,2,(X)_(1),(X)_(2)独立,则_(i)sim N(0,1), =1,2,(X)_(1),(X)_(2)()A
3.设 approx N(0,(4)^2), approx N(1,(3)^2), 且 (rho )_(x)=-dfrac (1)(2), 令 =dfrac (