的概率分布列和数学期望. 
的概率分布列和数学期望. 解:依题意,ξ的可能取值为0,10,20,30,40,50,60,其概率分别为
P(ξ=0)=0.22×0.52=0.01,
P(ξ=10)=×0.8×0.2×0.52=0.08,
P(ξ=20)=
×0.82×0.52+
×0.22×0.52=0.18,
P(ξ=30)=
×0.8×0.2×0.52=0.16,
P(ξ=40)=
×0.82×0.52+
×0.22×0.52=0.33.
P(ξ=50)=
×0.8×0.2×0.52=0.08,
P(ξ=60)=0.82×0.52=0.16
ξ的分布列为
ξ | 0 | 10 | 20 | 30 | 40 | 50 | 60 |
P | 0.01 | 0.08 | 0.18 | 0.16 | 0.33 | 0.08 | 0.16 |
ξ的期望
Eξ=0×0.01+10×0.08+20×0.18+30×0.16+40×0.33+50×0.08+60×0.16=36