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Re: [Phys-l] probability problem



"The Whites have two kids, at least one of which is a boy: what is the probability that they are both boys? The Browns have two kids, the older one of which is a boy: what is the probability that they are both boys?” The answers are again different in all 3 cases (1/4, 1/3, and 1/2 respectively)."


I suggest Carl should add: and assume statistical independence.

Here's some selection info.

http://www.amazingpregnancy.com/pregnancy-articles/74.html


bc used another method (pH)

p.s. one site was "all over the map" from ~ 50/50 to, if genetically influenced, 70/30 the same sex. One report was four girls before, finally!, a boy. This, of course, is statistically highly probable**. [.5^4 * .5, no?], and, therefore, suspect (70/30).

** assuming 50/50 and independent.

On 2010, Jun 30, , at 06:49, Carl Mungan wrote:

I like to summarize and write up matters. (Otherwise I forget them later.)

I have read over the posts of the past few days and rewritten the
problem and solution posted at:

http://usna.edu/Users/physics/mungan/Scholarship/TwoAces.pdf


possibly foolishly disregarding John Denker's remark that it's very
hard to write a probability question to give a desired answer.

Those interested are welcome to look and see if that writeup is an
adequate summary. Note in particular the additional acknowledgements
in the final paragraph. -Carl
--
Carl E Mungan, Assoc Prof of Physics 410-293-6680 (O) -3729 (F)
Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-1363
mailto:mungan@usna.edu http://usna.edu/Users/physics/mungan/
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