🚀 go-pugleaf

karr@cs.cornell.edu (David Karr) writes:

>>You meet the daughter of a friend of yours on the street.  You know
>>that your friend has two children.  You think to yourself, "Ignoring
>>the occurrence of twins, and sex-linked differences in birth rates
>>and infant mortality, what are the odds of this girl's sibling also
>>being a girl?"

One half - The probability of the other child being a girl is totally
independent of the sex of the first. The first child being
a girl does affect the 50-50 boy-girl distribution of the second (or any 
other) child.

Even if your friend had 10 children, and you met nine of them in the street,
all girls, then the probability of the tenth being female is still one half.

Of course, the probability of having ten girls is 1/1024 (assuming no
genetic oddities), but the probability of any one child being a girl is
one half

Christopher Hicks
--
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 Christopher Hicks    |    If it doesn't fit...
 cmh@uk.ac.cam.eng    |                        ...you need a bigger hammer.
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