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Do men or women have more brothers?

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Re: Do men or women have more brothers?

#61

Post by qbrass »

tehwalrus wrote: post #56

If every family only has one child, nobody has any brothers; the results are equal at 0 average brothers. If we take some distribution over size n of the families, say a distribution where family size is either 1 or 2, then the 1-size families don't contribute (they add a zero to the fraction, dragging the probability down in a systematic way equal for both sexes), and the 2-size families have four equally probable o…

> * males are more likely (~51% of births naturally, higher thanks to sex-selective terminations in China and India.)

In China, there may be more sons, but they're not likely to have brothers.

> * males die more frequently at younger ages, so older people will have fewer brothers than younger people.

Most people still consider dead siblings to be siblings.

Re: Do men or women have more brothers?

#62

Post by kqr »

mudbungie wrote: post #51
kqr wrote: post #47

Earlier quoted context omitted.

I'm surprised you managed to make it that complicated! http://pastebin.com/fck8qkMc

I like your solution! Good use of iter(). You actually bring up an interesting question of design philosophies. I thought that the script that I posted was extremely explicit, and therefore clear. Yours is far more terse, and implicit, which means that there's less to understand, but there is some onus on the reader to decode what is happening. I'm not sure which is better, as a policy. Obviously, solving problems wi…

It is as they say: every problem can be solved with an additional level of indirection... except the problem of too many levels of indirection.

Re: Do men or women have more brothers?

#63

Post by dhimes »

tempestn wrote: post #59
dhimes wrote: post #55

Earlier quoted context omitted.

Very cool- thank you for getting me to think about this. I get your results if you answer the question for any given sibling group (say, M M F, for example) Number of male brothers of males = 1 each * 2 Males = 2 Number of male brothers of females = 2 each * 2 Females = 2 and proceed to add all of those. In other words, if you weight the count by the number of siblings that have that count. If you just add up, for an…

In any given family of siblings that has both boys and girls, by definition the females will have more brothers than the males, yes. But it doesn't follow that "odds are that a given female has more brothers than a given male". The reason is that not all families have both. Families with multiple boys and no girls will bring the average up for boys. Families with multiple girls and no boys will bring it down for girl…

Nice. Thanks.

Re: Do men or women have more brothers?

#64

Post by xadhominemx »

squidfood wrote: post #36
xadhominemx wrote: post #31

Earlier quoted context omitted.

Well if you assume some sort of practical limit to the number of children a couple can have, then you end up with more B.

Actually, no. If you have a hard limit, then some people will end up A,A, ... A with no B. That evens it up again.

True

Re: Do men or women have more brothers?

#65

Post by ewjordan »

perilunar wrote: post #60
ewjordan wrote: post #52

Like tempestn noted in another comment, enumeration is straightforward for small families, and makes it crystal clear that for any family size N, boys and girls have the same average number of brothers: Gender: B G # brothers: 0 0 B avg # brothers: 0 G avg # brothers: 0 Gender: B,B B,G G,B G,G # brothers: 1,1 0,1 1,0 0,0 B avg # brothers: (2 + 0 + 0) / (2 + 2) = .5 G avg # brothers: (0 + 2 + 0) / (2 + 2) = .5 Gender:…

You are assuming that for a family of N kids, each permutation is equally likely. As others have pointed out, that is not the case.

This is a late reply because I missed this until now, but if you accept the typical parameters of a statistical thought experiment, you should assume that the permutations are equally likely. The real world nastiness of biology and society fouls that up, but thought experiments like this are never intended to be about not picky real world details, boy/girl is always assumed to be a coin flip. (Not to say that real world results are not interesting as well)

And there are a half dozen arguments in this thread that claim to disprove this result even if they accept the coinflip hypothesis - it's really those that I take issue with.

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