一、填空题-|||-1.设总体X的一组样本观测值为-|||-1.4 2.3 1.8 3.4 2.7-|||-则样本均值 overline (x)= __ 样本方差 ^2= __ .-|||-2.设总体X服从正态分布N(2,5),(X1,X2,···,X10)为其样本,则样本均值UND的分布-|||-为 __ .-|||-3.设总体X服从具有n个自由度的x^2分布,(X1,X2,···,Xn)为其样本,X为样本均值,则-|||-有 (overline (X))= __ (overline (X))= __ .-|||-4.设总体 approx N(mu ,(sigma )^2), (X1,X2,···,Xn)为其样本,X、S^2分别为样本均值和样本方差,-|||-则有 x~ __ dfrac ((n-1){S)^2}({sigma )^2}approx __ dfrac (x-1)(5)- __ .-|||-5.设总体 approx N(1,4), (X1,X2,···,X5)为其样本,令-|||-=a(({x)_(1)-(x)_(2))}^2+b((2{x)_(3)-(x)_(4)-(x)_(5))}^2-|||-则当 a= __ b= __ 时有 approx (x)^2(2).