§7.5正态总体均值和方差的区间估计 n(, 又s)='2x-} 于是)=Ek,a-r] 4 = a(n-DPE(S2) =t。2(n-10'σ2. 21/48 [ ( 1)] , 4 2 / 2 2 2 t n n S L n i Xi X n E E 1 2 2 ( ) 1 1 又 (S ) §7.5 正态总体均值和方差的区间估计 , 2 [ ( 1)] 4 ( ) 2 / 2 2 2 t n n S 于 是 E L E [ ( 1)] ( ) 4 2 2 t / 2 n E S n [ ( 1)] . 4 2 2 t / 2 n n 21/48