Question

已知事件A和B的概率分别为Pa=0.8,p(b)=0.6,且p(b-a)=0.2,求p(B/A)？

Answer 1

P(AB)=P(B)-P(B-A)=0.6-0.2=0.4
P(B/A)=P(AB)÷P(A)=0.4÷0.8=0.5
P(B-A)是B发生但A不发生的概率
P(AB)是AB都发生的概率
P(B/A)是A发生前提下B发生概率、

Answer 2

简单分析一下，详情如图所示

Answer 3

P(A) =0.8 , P(B)=0.6, 且P(B-A)=0.2 求P(B|A)
solution:
P(B-A)=0.2
P(B)-P(A∩B) =0.2
0.6-P(A∩B) =0.2
P(A∩B) =0.4
P(B|A)
=P(B∩A)/P(A)
=0.4/0.8
=1/2