SirBomber: LOL

Hooman:

What you are saying is this:

the chances of any of the 4 possibilities is obviously 25%:

BB : 25%

BG : 25%

GB : 25%

GG : 25%

Everyone should be able to agree with me on this one (not taking into account the 52:48 ratio).

So going with this, there is a 25% chance for both kids to be a girl, correct?

Now, you are saying is that if you know the sex of one of them, the natural chance of the GG combination suddenly changes?? Chances don't change with new information about an existing situation. The chance for both of them being a girl is still 25%. It always will be, since there's a 50:50 ratio for sex.

Based on the question at hand "what is the chance of the OTHER one to be a girl", the question is about one specific event, NOT both births, and the answer is a simple 50:50 chance as it is for any child being born on this planet.

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Now, let's review the following situation:

Q1: A woman gives birth to a girl. She gets pregnant again. What is the chance of this second baby to be a girl as well? Is it 33%, or is it 50%

(i'll leave this question open for you to answer).

Q2: A woman gives birth to 2 children. The second baby was a girl. What is the chance of the first one being a girl? Is it 33%, or is it 50%

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As i said before: new information does not chance an already calculated chance. Here's another example, in which i will provide new information, but in doing so, change the situation at hand (in which case the answer to the problem changes with it):

There's 100 randomly selected women, all of them have 2 children.

Chances are that 25 of them have 2 girls. Another 25 have 2 boys, and the rest (50) have a boy and a girl. This would illustrate my answer of 25%.

Now let's

change the situation: let us select all the women that have at least one girl and discard the others: you are left with a

**DIFFERENT** sample of only 75 women, since the other 25 have no girls.

This changes the answer to your 33%, although it is still the same 25 women we are talking about.

The essence here is that the sample has changed from 100 to 75, so the 2 answers cannot be compared with each other as they are from 2 totally different situations.

The question that simpsonboy asked is about 1 woman. The sample never changes, not even when i say one of the kids is a girl.

The simple fact remains that any person being born has a 50% chance of being female, no matter what the sex of his/her siblings is. Not even if he/she has 100 siblings (theoretically speaking).