b***k
发帖数: 2673 | 1 ☆─────────────────────────────────────☆
kaofaint (haha) 于 (Tue Dec 11 21:05:13 2007) 提到:
today, a guy called me and asked the following question
My parents have two children, what's the probability that I have a brother?
I was confused, shouldn't the answer be 1/2? What I though was that the fact
he is a guy is independent with the gender of the other child. But it seems
the guy is not happy with my answer. What's the trick here?
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orion (M42) 于 (Tu | h*****n
发帖数: 38 | 2 I don't think it is right.
If you are asked, if you know for a 2 children family, one children is boy,
what is the probability that the other one is also a boy? the answer is 1/3.
and then the
interviewer would say "oh, I forget to say that you are the boy! I am your
father, we live in Iceland. ", now you change you answer to 1/2? It makes no
sense... How does that extra information even relate to the problem? |
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