Newsgroups: rec.puzzles
From: hoey@aic.nrl.navy.mil (Dan Hoey)
Date: 1995/12/09
Subject: Re: ASK MARILYN

jud.mccra...@swsbbs.com (JUD MCCRANIE) partially quotes the problem
posed in M vos Savant's column, which read in full:

  "Suppose you're on a game show, and you're given a choice of three
  doors.  Behind one door is a car; behind the others, goats.  You
  pick a door--say, No.1--and the host, who knows what's behind the
  doors, opens another door--say, No.3--which has a goat.  He then
  says to you, 'Do you want to pick door No.2?'  Is it to your
  advantage to switch your choice?"

> I believe that it is implied that the choice is always offered.
> (I believe that was the way it was done on the TV show).

I quoted it in full to make it clear that no such implication is
expressed in the problem statement.  As for the way it is done on the
TV show, I do not recall seeing any situation like this on the show,
and I've heard reports of interviews in which Monty Hall said that
such straightforward re-dealing was never done.  So there seems to be
no precedent on the TV show to support such an implication.

> Sure, it is sloppily written, and is not a precise enough statement
> of the problem, but when I first read it years ago my interpretation
> was that he always offered you the chance to change.

Perhaps you read a different problem years ago, and are allowing your
recollection of it to color your perception of this one.  As I weary
of pointing out, there are two distinct problems, the "classic" one in
which the host is required to offer a choice and the "common" one in
which the host is not required to offer a choice.  I really can't see
why anyone who realizes and understands the difference would classify
this one as the former.

Dan Hoey                   posted and e-mailed
Hoey@AIC.NRL.Navy.Mil