On Mar 11, 6:56 pm, Steven <sgottlie...@hotmail.com> 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.