Math T-probability!!!!

jenny_kam

请问哪一个高手会做？？？


Two porcelain factories A and B produce cheap china cups in equal numbers. If closely examined, a cup from A will be found flawless with probability 0.75, but one from B with probability 0.5. James picks up two cups from a batch in a shop. The shopkeeper says that all the cups in the batch come from the same factory, but the batch is equally likely to come from factory A or from factory B.
QUESTION: James drops the second cup before he can examine it. Given that the first cup was flawless, find the probability that the second cup was also flawless before the accident.

peaceboy

ans =  0.40625？

答案来先我才想

woeifang

ans = 0.65?

答案来先我才想

sunsilk_cv

答案来先我才想

jenny_kam

0.625....

peaceboy

回复 8# 50912cmea


   表根据我的答案修改题目pls

peaceboy

算了算，支持3楼的答案

50912cmea 怎么删帖了？

50912cmea

算了算，支持3楼的答案

50912cmea 怎么删帖了？
peaceboy 发表于 30-7-2011 02:06 PM

也同意3楼的答案

NeoHom

0.40625 还没除于 0.625。 0.40625 是general probability.

lokejiunnwoei92

Solution : (0.50*0.75) + (0.50*0.50)
用tree diagram ...来自A and B factory 是一样所以是0.5 和 0.5
然后A 的0.5 里面完美的有0.75 和 B的0.5里面完美的有0.5

p/s:如有错请更正

leong321

P(2nd f l 1st f)=P(2nd flaw n 1st flaw)
                        P(1st flaw)
                      =0.5(0.75)(0.75)+0.5(0.5)(0.5)
                        0.5(0.75)+0.5(0.5)
                      =0.65