Looks like your P(B), P(A&B) are using different events

来源: 网恋无罪 于 2020-05-19 15:07:18 [] [博客] [旧帖] [给我悄悄话] 阅读数 : (593 bytes)
回答: conditional probability: 由 redplum 于 2020-05-19 13:33:06

P（B）is using "marble pick" as event and color order matters;  whereas P(A&B) is using "bag pick" as event marble color picking order does NOT matter.

P(A&B) using "marble pick" as event and color order matters={白白}/ {白白，白黑，黑白，黑黑}=1/4

P(A|B) = P(A&B)/P(B)=（1/4） /（ 1/2）=1/2    ！

 

 

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