1.设 approx N(2,18), 若 Y=(B) ),则 approx N(0,1).-|||-(A) dfrac (x-2)(18): (B) dfrac (x-2)(3sqrt {2)} (C) dfrac (x+2)(18): (D) sqrt (2)X+2.

[题目]设 approx N(0,1), 令 =-x-2, 则 Y~ ()-|||-

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

函数(x)=dfrac (1)(x-2)的间断点是(x)=dfrac (1)(x-2)(x)=dfrac (1)(x-2)、(x)=dfrac (1)(x-2)

设连续型随机变量 X - N ( 1 , 4 )， 则 dfrac (x-1)(2)approx (A N ( 0 , 2 ) B N ( 1 , 2 ) C

1.设总体 approx N(1,9), X1,X2,···,x9是来自总体X的一个样本,则 ()-|||-(A) dfrac (overline {X)-1}

5、已知随机变量X的密度函数为 (x)=dfrac (1)(2sqrt {2pi )}(e)^-dfrac ({(x-1)^2)(8)}, 则 =dfrac (

设X与Y相互独立,且approx N(1,2), _(Delta )N(0,1),令approx N(1,2), _(Delta )N(0,1),则D(Z) =

1.-|||-设 approx N(0,1), 则 =3x-1 服从 ()-|||-A approx N(0,1)-|||-__-|||-B approx N(

设服从参数为2的泊松分布，则 |X-2|leqslant dfrac {sqrt {2)}(2)} =( ) () |X-2|leqslant dfrac {

4.10 设随机变量X 1,X2,X3相互独立,且 _(1)approx B(4,dfrac (1)(2)) _(2)approx B(6,dfrac (1)(