Current Events > If a family has two children and you already know one of them is a girl.

(+) Yeah! (+)

Then what is the probability that the second child is also a girl?

You don't speculate. Final answer.
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It's 50% or what ever the typical distribution favoring X-sperm over Y-sperm is.

That depends if you calculate them separately or goes out of the way with what are the chances to give birth to two females which is not related to this question BS.
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The child is a planet and the Y chromosome bus a room outside

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You have to think outside the box
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50%

P(A|B) only applies if known event B can directly influence the outcome of A, that is A is not independent of B.
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Assuming a single child has an equal chance of being either a boy or a girl, I want to say the answer is 1/3. If I'm thinking about it correctly, there are three situations in which we can know one of the kids is a girl. In two of those situations the other is a boy. Only one scenario contains two girls.

This is very similar to a question somebody here asked a while ago where you had to count the number of scenarios with the given information. I got it before, but there was a debate over the wording of the question.

Paragon21XX posted...

50%

P(A|B) only applies if known event B can directly influence the outcome of A, that is A is not independent of B.

It's actually not uncommon for women to be e.g. allergic to testosterone or have other kind of unknown conditions that influence likelihood of which sex the baby is.
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Overall Possibilities:
1 = B, 2 = B
1 = B, 2 = G
1 = G, 2 = B
1 = G, 2 = G

We know one of them is a girl, so the first possible combination is ruled out. Of the remaining 3 options, only 1 of them has a second girl.

Therefore it is 1/3.
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Since it's asking the probability that the SECOND child is a girl, knowing only that ONE of the children is a girl, the answer is 2/3
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50%

/Topic
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0%

you said one of the children, not at least one of the children
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konokonohamaru posted...

Since it's asking the probability that the SECOND child is a girl

I think he worded the question poorly. He should have said "other" instead of "second" as knowing one of the kids is a girl is different than knowing the first kid is a girl. The question in the topic title conflicts with that in the post, unless you know what he's getting at.