例 (1)代入(2,得: b-a)1 ∑X2-X2=S2 n i=1 b-a=2√3S a+b=2X 解得:a=X-√3S b=x+√3例 13 ˆ 3 n 解得：a X S = − 2 2 2 2 1 ( ) 1 12 n i n i b a X X S n = − = − =  2 3 n  − = b a S a b X + = 2 ˆ 3 n b X S = + (1) 代入 (2), 得： ˆ 3 n 解得：a X S = − ˆ 3 n b X S = +