§3 随机变量的分布函数 PX≤=r=4 x P2≤X≤3} =F(3)-F2)+PX=2, -1-313 424?, 4 1 ) 2 1 } ( 2 1 P{X  = F = , 2 1 4 1 4 3 ) 2 3 ) ( 2 5 } ( 2 5 2 3 P{  X  = F − F = − = , 4 3 2 1 4 3 1 (3) (2) { 2} {2 3} = − + = = − + =   F F P X P X -1 0 1 2 3 x 1 §3 随机变量的分布函数