Re: Fun With Bayes' Theorem

From: Lee Corbin (lcorbin@ricochet.net)
Date: Sun May 13 2001 - 20:57:23 MDT


Eliezer Yudkowsky wrote:

> Out of all the parents who *could* say "At least one of my children is a
> girl", 2/3 of them have a boy. Out of all the parents who *do* say "At
> least one of my children is a girl", 1/2 of them have a boy.

I am sufficiently innocent of Bayesian statistics that I have to
admit that anything is possible; if you're right, then there is
a demarcation between what mathematicians would or should say,
and what statisticians could or do say. :-)

But why are the parents who *do* say "At least..." different than
the parents who *could* say it? The earlier idea, who *could* truthfully
say what, seems much easier to grasp. As for what people do say, this
would seem to me to depend a great deal upon the particular situation.
One easily contrives a situation where even under *do* I'm right: King
Harod orders everybody who could say it to go to a mathematician and
actually say it, etc. What situations do you have in mind where

> Out of all the parents who *do* say "At least one of
> my children is a girl", 1/2 of them have a boy.

Lee Corbin



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