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Topic: probability question
Replies: 9   Last Post: Mar 13, 2008 4:08 PM

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Posts: 1,677
Registered: 12/1/07
Re: probability question
Posted: Mar 12, 2008 12:00 AM
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On Mar 11, 6:56 pm, Steven <> wrote:
> Suppose you meet me on a street corner and I introduce you to my son who is with me. I inform you that I have another child at home. What is the probability that my other child is a girl.
> I looked at the sample space which I claim is bb, bg, gb and so the answer is 2/3. Is this correct?
> Steven

Yes, provided that you don't say which child is older. If you do say
which is older, the probability becomes 1/2! You can also look at the
problem this way: you toss a coin twice and announce that you got at
least one Head. What is the probability the other outcome was a Tail?
Again, the probability that the other outcome is a Tail is 2/3 if you
don't say whether your announced Head was first or second, and is 1/2
if you do announce its position.

R.G. Vickson

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