A woman has two kids, one of them is a girl

**Janszoon** · 03-04-2013, 10:09 PM

Quote:

Originally Posted by Pedestrian

Do those recorded births only take into account infants after a certain age, or is it possible that infantcide could make up the 14+ point difference?

This topic is piquing three of my academic interests at once.

I think it's based on the gender at birth, but I don't really know. This seems to indicate that it's a naturally occurring phenomenon.

midnight rain · 03-04-2013, 10:23 PM

Quote:

Originally Posted by Janszoon

I think there are more women in the world than men, because women have a longer life expectancy, but when it comes to babies I believe there are males than females.

According to Wikipedia:

I think the tendency of certain countries to abort females and not males is what's actually skewing those numbers.

Anyways it was meant more of an out of the box problem, with the emphasis on the wording of the question. If I had asked, "A woman has 2 children, the first baby was a female. What are the chances the second one is also a female?" THEN the answer would be 50%

**Janszoon** · 03-04-2013, 10:24 PM

Quote:

Originally Posted by Tuna

I think the tendency of certain countries to abort females and not males is what's actually skewing those numbers.

I'd imagine if that were the case it wouldn't be the scientific mystery that it is.

Face · 03-05-2013, 04:18 AM

Quote:

Originally Posted by Tuna

more productive than that 'MB was so much better back in the day' delusion youve been under

answer is 33% cause there's four different possibilities:

BG
GB
BB
GG

Because one of them is already a girl, that dismisses the possibility of BB, leaving:

BG
GB
GG

Since one of them is already a girl, 1/3 chance the other will also be a girl (GG)

That isn't right...but then I though about it and it also made sense, but my answer wasn't wrong (!)

So I got frustrated, looked it up, and it's how the question is interpreted. There's a long article covering the different analysis..
Boy or Girl paradox - Wikipedia, the free encyclopedia (note in the article they switch the boy/girl)

Quote:

From all families with two children, at least one of whom is a boy, a family is chosen at random. This would yield the answer of 1/3.
From all families with two children, one child is selected at random, and the sex of that child is specified. This would yield an answer of 1/2.[3][4]

Interpretation1: out of all families with two children with at least one girl, what are the chances of selecting one with two girls? 1/3

or

Interpretation 2: A family with 2 children is selected, one is found to be a girl, what are there being two girls? 1/2

Cinnamonics · 03-05-2013, 10:11 AM

Well, normally I would say 50%, disregarding biological factors, but you used the word "also", which makes me say 25%. From what I remember of probability math, it should be 0.5 x 0.5.

View Poll Results: What are the chances the other is also a girl?
0%	1	9.09%
25%	0	0%
33%	4	36.36%
50%	5	45.45%
100%	1	9.09%
Voters: 11. You may not vote on this poll

03-05-2013, 10:11 AM	#45 (permalink)
Cinnamonics Music Addict Join Date: Dec 2012 Posts: 117	Well, normally I would say 50%, disregarding biological factors, but you used the word "also", which makes me say 25%. From what I remember of probability math, it should be 0.5 x 0.5.