Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site umcp-cs.UUCP
Path: utzoo!linus!decvax!harpo!seismo!rlgvax!cvl!umcp-cs!mark
From: mark@umcp-cs.UUCP
Newsgroups: net.math,net.misc,net.rec.bridge
Subject: Re: simple (?) statistics problem solved
Message-ID: <2039@umcp-cs.UUCP>
Date: Sat, 20-Aug-83 21:55:01 EDT
Article-I.D.: umcp-cs.2039
Posted: Sat Aug 20 21:55:01 1983
Date-Received: Sun, 21-Aug-83 07:18:18 EDT
References: <657@vax2.UUCP> <2034@utcsrgv.UUCP>
Organization: Univ. of Maryland, Computer Science Dept.
Lines: 28

I think the difference between the 50/50 and the 1/3-2/3 views
is exactly the rescan issue (as Laura says).  

The crucial difference is whether or not it is assumed that the
open drawer was opened at random.  If it was, then it could have
been any one of the three gold drawers, and the probability that
the other drawer in the same cabinet is gold is 2/3 (by everyone's
arguments which need not be repeated.)

However, if all you know is that a drawer stands open and
the other drawer could be either gold or silver, then the
50/50 result follows.  BUT--this conclusion ignores some
of the relevant informatin and so is a less accurate conclusion
than the one using all the given prior information.

An even better guess could be made if you knew something about
the "random" process used to pick tl%drawer, such as it
was really a psychology professor doing an experiment on
perceived probabilities or someone with X-ray vision who
hated (or liked) you.  Assuming a random event is a convenient
approximation to having no knowledge, but it is never exactly right.

opening-- 
spoken:	mark weiser
UUCP:	{seismo,allegra,brl-bmd}!umcp-cs!mark
CSNet:	mark@umcp-cs
ARPA:	mark.umcp-cs@UDel-Relay