today's fun with probability
Nov. 20th, 2002 07:33 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
eub1) You meet a man at the bowling alley [this is how it was posed, honest]. He has two children, bowling on lane 17. You see one girl there; the other child doesn't happen to be visible.
2) Man, bowling, two children. You ask if he has any daughters. He says yes.
In each case (any difference?), what's the probability that he has two daughters?
Assume male and female are mutually exclusive and 50-50 and independent between children. Make any further assumptions you need.
[edit: spoilers in comments, natch]
2) Man, bowling, two children. You ask if he has any daughters. He says yes.
In each case (any difference?), what's the probability that he has two daughters?
Assume male and female are mutually exclusive and 50-50 and independent between children. Make any further assumptions you need.
[edit: spoilers in comments, natch]
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Re: do not taunt happy fun mathchick
Date: 2002-11-20 11:51 pm (UTC)In my (4) scenario, I'd want to talk about the events "2^0 bit is high" and "2^1 bit is high" for x uniform from {1, 2, 3}. Call those C and D. C and D are not independent, right? P(C) = P(D) = 2/3; P(C and D) = 1/3.
A and B, to be independent, would be those bit highnesses for x from {0, 1, 2, 3}, maybe? I don't remember exactly how this machinery works -- do we then talk about the independence (the lack thereof) of "A and not x=0" and "B and not x=0", or what?