2009-03-12, 01:20 PM
Pistolero831 Wrote:definitely 25%. 1/2 times 1/2 is 25%. Assuming there's nothing freaky going on with the genes that makes it less or more likely to get 2 boys in a row.
We already know that one of them is a boy, which means it's not one half times one half.
Though yeah, you're right Opeth.
We have the following chances (as you said)
BB
BG
GB
GG
Now, stating that this woman has got two children, we know that all the different combinations above works. We assume 50% for both chances, in case anyone wonders. Now, we are given that one of the children is a boy. That eliminates GG, and leaves us with 3 different combinations. only one of them gives BB, thus BB = 1/3 in this case.
I don't like how these things are stated though. I mean, usually, I'd think "oh, the first one is a boy" when seeing "One is a boy. What are the odds the other one is a boy as well?"
Basically, when you know for sure one child is a boy, you can leave it out. However, when you know that one of the children is a boy, that's when you'll do stuff liek dis.