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

Key · 03-04-2013, 01:38 PM

50%. She'll either have a boy or a girl.

Paedantic Basterd · 03-04-2013, 09:50 PM

I see.

The question we're being asked is about the odds of two disjoint events occurring together (Girl 1 followed by Girl 2), not the probability of a single event (the birth of either a boy or a girl).

I'm not sure if we can assume that biologically, inheritance of the X or Y is an even 50/50 split, since more women are born in the world than men, but I see where this is going.

**Janszoon** · 03-04-2013, 09:53 PM

Quote:

Originally Posted by Pedestrian

I see.

The question we're being asked is about the odds of two disjoint events occurring together (Girl 1 followed by Girl 2), not the probability of a single event (the birth of either a boy or a girl).

I'm not sure if we can assume that biologically, inheritance of the X or Y is an even 50/50 split, since more women are born in the world than men, but I see where this is going.

I think it's the reverse actually, as I mentioned above. Either way the point still stands that it's not 50/50.

Paedantic Basterd · 03-04-2013, 09:54 PM

It's entirely possible I'm incorrect, but I do believe I recently covered this in my studies somewhere.

Anyone else want to weigh in?

**Janszoon** · 03-04-2013, 09:58 PM

Quote:

Originally Posted by Pedestrian

It's entirely possible I'm incorrect, but I do believe I recently covered this in my studies somewhere.

Anyone else want to weigh in?

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:

Quote:

In 2010, the global sex ratio was 986 females per 1,000 males and trended to reduce to 984 in 2011.

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.

Paedantic Basterd · 03-04-2013, 10:01 PM

Oh, okay. Interesting, I sort of figured it'd be the other way around since there are more Xs kicking around in the gene pool than Ys. Wonder why that is.

**Janszoon** · 03-04-2013, 10:03 PM

Quote:

Originally Posted by Pedestrian

Oh, okay. Interesting, I sort of figured it'd be the other way around since there are more Xs kicking around in the gene pool than Ys. Wonder why that is.

I don't know. It is definitely weird.

Burning Down · 03-04-2013, 10:07 PM

Quote:

Originally Posted by Pedestrian

Oh, okay. Interesting, I sort of figured it'd be the other way around since there are more Xs kicking around in the gene pool than Ys. Wonder why that is.

That wouldn't determine the ratio of women to men though, since women are supposed to have two X chromosomes and men determine the gender of their children, so then there are only as many X sperm around as there are men in the world.

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

03-04-2013, 01:38 PM	#1 (permalink)
Key . Join Date: Dec 2010 Posts: 13,153	50%. She'll either have a boy or a girl.

03-04-2013, 09:50 PM	#2 (permalink)
Paedantic Basterd Music Addict Join Date: Sep 2010 Posts: 5,184	I see. The question we're being asked is about the odds of two disjoint events occurring together (Girl 1 followed by Girl 2), not the probability of a single event (the birth of either a boy or a girl). I'm not sure if we can assume that biologically, inheritance of the X or Y is an even 50/50 split, since more women are born in the world than men, but I see where this is going.

03-04-2013, 09:54 PM	#4 (permalink)
Paedantic Basterd Music Addict Join Date: Sep 2010 Posts: 5,184	It's entirely possible I'm incorrect, but I do believe I recently covered this in my studies somewhere. Anyone else want to weigh in?

03-04-2013, 10:01 PM	#8 (permalink)
Paedantic Basterd Music Addict Join Date: Sep 2010 Posts: 5,184	Oh, okay. Interesting, I sort of figured it'd be the other way around since there are more Xs kicking around in the gene pool than Ys. Wonder why that is.