例1RV.X的分布律为 0 1 2 Pk 0.30.60.1 求X的分布函数(x)并求P{1<X≤2},F(0.5)及PX=0.5} 解F(x)=PX5x}=∑PX=x} k ≤x x<0. P{X=0}=0.3 0≤x<1, P{X=0+PX=1=0.9,1≤x<2解 F(x) = P{X  x} 例1 R.V. X的分布律为 求X的分布函数F(x)，并求P{1 X  2},F(0.5)及P{X = 0.5}. pk 0.3 0.6 0.1 X 0 1 2   = = x k x P X xk { }        = 0, x  0, P{X = 0} 0 x 1, P{X = 0}+ P{X =1} = 0.3, = 0.9, 1 x  2, 1, x  2