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#1




odds of having 11 children of the same sex
I just watched a TV show that had a woman who allegedly had 11 children, all boys. Am I right in thinking that the odds of this happening are 1 in 2 to the 11th power or 1/2048? Certainly statisticly possible, but also definitively unlikely.
Any replies are appreciated, AllFree
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If you are the only sane person in the room, everyone else says you are crazy. Have you ever noticed that the world is just one big room? 
#2




Your calculation is correct, assuming the odds of one gender over the other is in fact one in two. Studies have suggested this may not be the case, but it's close enough.

#3




How large is the bias and towards what sex? I imagine it must be small.

#4




About 105 boys are born for every 100 girls. Makes the odds against 11 boys in a row somewhat less unlikely.



#5




Your odds are only for all families with eleven children. This has to be multiplied by the odds of a family having 11 children of any sex.

#6




There also appears to be a small bias toward one gender or another dependent on the gender of previous children  particularly if you have had boys, but only very slightly:
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Grim 
#7




Also assuming that there isn't a biological reason that Y bearning sperm are not being favored for that specific couple.

#8




This is the important point. There are plenty of couples who are biologically incapable of producing children of one sex or the other. Doesn't matter how many kids they have, they will always be all the same sex.

#9




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#10




I knew, even before opening this thread, that it had already degenerated into pointless nitpickery. By any reasonable standard, the answer is 1 in 2^11. Let it go, people. Let it go.

#11




My aunt quit after 6 boys.

#12




I think we're gonna need a cite for that.

#13




Actually, it's 1 in 2^10. The odds that your first kid has some sex (1) multiplied by the odds that the next ten have the same sex as the first one (1/1024).
Last edited by Sofis; 05072010 at 06:48 AM. 
#14




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Dammit, now I'm pointlessly nitpicking! 


#15




If you read the thread title, there's a hint that, I feel, clears up this ambiguity.

#16




If daddy, biologically, can't throw that X chromosome, it will be "boy" everytime.

#17




What the heck does this mean? The odds that a family with 11 children has 11 children of any sex is 100%.
Last edited by CookingWithGas; 05072010 at 08:49 AM. 
#18




It may be worth noting that the chance of getting on a TV show devoted to the interesting distribution of the sex of your 11 children improves if they are all boys.

#19




Needscoffee wrote:
Your odds are only for all families with eleven children. This has to be multiplied by the odds of a family having 11 children of any sex. I think Needscoffee meant something like "What are the odds that any two people who start having kids will end up with exactly 11 kids of the same gender". (I presume that this is a misunderstanding of the original question, which presumably is "Given that a couple has 11 kids, what are the odds that all 11 will be the same gender".) Last edited by cjepson; 05072010 at 09:28 AM. 


#20




My mother was the youngest of nine girls.

#21




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Suppose someone says that "The odds of a family having 3 children who are all boys is 1/8." Taken literally, that would mean that 1/8 of all families ought to have exactly 3 boys and 0 girls. But that's not true. Lots of families have fewer than 3 kids, or more than 3 kids. A more correct statement would be that "If a family has exactly 3 children, the odds that they are all boys is 1/8." And if X% of all families have exactly 3 children, then the odds of a family having 3 children who are all boys is (X%)*(1/8). 
#22




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But, as I say, I've never heard of that happening. 
#23




More nitpickery:
There is also the issue of identical twins. If some among the 11 are identical twins then they should be counted as a single unit rather than 2 individuals in the calculations. 
#24




True, but then you have to factor in the probability of twinning.



#25




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"Mr. Gellatly found evidence that men carry a gene that determines the percentage of X and Y chromosomes in their sperm, and that the gene comes in three alleles, or versions. One produces mostly X chromosomes, another mostly Y, and the third yields equal numbers of both." 
#26




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#27




The question that somebody SHOULD be asking is statistical rather than probabilistic  how many children of identical gender does one couple have to produce before you reject the notion that each conception FOR THAT COUPLE is an independent event with probability 0.5 of producing a child of either gender?

#28




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#29




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That's just a hypothetical case; I don't know of any specific examples of such a situation. 


#30




I come from a family of five girls. Everyone I know with kids has one sex only, no mixed bags. The idea that men produce one sex over the other and resist regular probability seems plausible to me.

#31




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#32




Removed for another thread.
Last edited by Cat Whisperer; 05072010 at 11:25 AM. 
#33




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#34




If the parents are biologically incapable of having any kids at all, then the kids they don't have may be of either sex.



#35




If I do that, will my post count get that high too?

#36




There is a link between the sex chromosome contained in a sperm and its motility, though I'm not well enough versed in the science to really be able to sum it all up. I think Xchromosome sperm tend to live longer (giving a longer window for successfully fertilizing an egg) but also tend to be slower (giving the boys a chance to get there first). Or perhaps it's the other way around.
So it doesn't have to be a matter of certain sperm not being viable, but rather that certain sperm have a lower chance of fertilizing an egg than others based on its "sex". This is probably also strongly affected by the woman as well; the environment the sperm find themselves in will affect their survival and motility. Anecdotally, I know of a family with 4 boys, but when the man remarried after a divorce, his new wife had 2 daughters by him. 
#37




First we must assume all the children are spheres.

#38




No, but if you feel the need to follow every joke post you don't like with a post, you'll be up there in no time.

#39




For statistical purposes on a large population, the odds are generally considered 5050 for either gender. (In actuality, there is a slight (about 5%) bias toward males, and a very small number who fit both or neither category).
But for any specific couple, there can be a significant bias toward either gender. Anecdotal stories of this are common. Personally, I know a neighboring family who had 7 boys, then later 1 girl. Famous families of mostly one gender are numerous: the Andrews sisters, the Jacksons, the Kennedys, etc. This is well known in horse breeding. One of the common stats considered when evaluating a stallion is the gender percentage of his get. Last edited by Tim@TBonham.net; 05072010 at 04:41 PM. 


#40




A friend is the first of 8, 4 boys and 4 girls.

#41




My father was the oldest of 11 boys, no girls. Didn't seem to be a gender bias in the next generation, though.

#42




This is a common statistical mistake (maybe even has a name, but can't find it right now).
The equation that states "the odds of X occurring are 1:Y therefore the odds of X occuring N times is Y to the power of N", is only correct if the odds are always 1:Y. For most real world cases the odds of X occurring once may be 1:Y but once X has occurred the chances of it occurring again drop dramatically (and likewise for the third, fourth, etc. occurrence). Most likely as others have pointed out there is a genetic predisposition to producing children of a particular gender, so by the time she had 10 kids that were all boys the chances of the 11th one being a boy are nowhere near 50:50. Last edited by griffin1977; 05072010 at 05:52 PM. 
#43




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#44




Not have kids? Very likely. You'll have more time for the Dope that way.



#45




WOOOO! I'm not having kids like a motherfuck!

#46




In a vacuum.
Incidentally, if there was some biological mechanism in play, it isn't necessarily on the father's side. I can imagine a woman who spontaneous aborts XY embryos while keeping XX ones (or viceversa) who may not even be aware of how many rejected embryos she is tossing. 
#47




If a woman has 10 male children, what are the odds that the 11th will be Hitler?

#48




I read somewheremaybe here?that having given birth to a child of one sex, you are slightly more likely to give birth to subsequent children of that same sex, whatever it is.
In other words, that there are slightly more families with multiple siblings of the same sex than with multiple siblings of both sexes. This is certainly true in my family. Among my cousins there is a preponderance of boys. But the one who had girls had ONLY girls. The rest had only boys. (I have four.) 
#49




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#50




You have never in your life met someone with kids of both genders?

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