概车纶与款理统外 2因为x-X2-xm-1, i- 于是g空-sa =Ps号2x-Ws8 =P{8≤x2(15)≤32 =P{x2(15)≥8}-P{x2(15)≥32}=0.98. 备用例题( ) ~ ( 1), 1 (2) 2 1 2 2  − − = X X n n i i   因为         −  = 2 1 2 2 ( ) 2 1 2   n i Xi X n 于是 P       =   −  = ( ) 32 1 8 1 6 1 2 2 i P Xi X  {8 (15) 32} 2 = P    { (15) 8} { (15) 32} 2 2 = P   − P   = 0.98 . 备 用 例 题