Re: interesting coin flip problem
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You're talking to a man you've never met before. He mentions that he has only one natural sibling. What the chances he has a brother? What the chances he has a sister?
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Well, if we're assuming that a parent is 50/50 to have a son or daughter, then the probability he has a sister is 1/2.
This is the same as scenario 2 in AaronBrown's post where you are told one specific result and have to find the probability of the other.
On the other hand, if a parent told you "I have two kids and at least one of them is a boy" then the probability that the other is a daughter is 2/3, like in the coin flipping examples given earlier in this thread.
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