它们的观察值分别为 x2=nx2 n-1 n-1 s=m-12(x-x10 它们的观察值分别为     = = = = − − =         − − − = − = = n i i n i i n i i n i i x x n s x nx n x x n s x n x 1 2 2 1 2 1 2 2 ( ) 1 1 ; 1 1 ( ) 1 1 ; 1