Question

某仪器主要由ABC三个元件组成,这三个元件出故障的概率分别为0.1,0.2 ,0.3.

Answer 1

P{X=1}=0.1*0.8*0.7+0.9*0.2*0.7+0.9*0.8*0.3=0.398

P{X=2}=0.1*0.2*0.7+0.9*0.2*0.3+0.1*0.8*0.3=0.092

P{X=3}=0.1*0.2*0.3=0.006

数学期望为：1*0.398+2*0.092+3*0.006=0.6