The Monty Hall Problem

by john on July 14, 2003

I haven’t seen the Monty Hall Problem mentioned for some time until it was recently brought up in rec.gambling.craps. I was all set to write up a little something on it until a Feedster search quickly discovered that it has been discussed at length recently, with active participation by commenters, by Brad Wilson (The .Net Guy) in The Let’s Make a Deal Paradox and I won’t go over that ground again, except to point his article out and provide a few more links.

The premise behind the Monty Hall problem is this: Given the choice of 3 doors you select one behind which exists a prize. After selecting the door you are shown the contents of another door, which does not contain the prize you seek. The question is should you switch to the last remaining door or keep your initial selection? Intuition would say it is a 50/50 shot so no advantage to switching, but intuition would be wrong.

This problem has tricked many a mathematician. Just ask Marilyn vos Savant, who started this whole mess by answering this question correctly (that you should switch) in a Parade Magazine article over a dozen years ago. Here is a pretty good summary of how that went. It looks like it took Marilyn a few different articles to convince the naysayers. Interestingly enough there are clear parallels between what Marilyn went through and some of the comments from Brad’s article. Some people just can’t suspend belief in their intuition!

Applet showing the problem in action.

Classic problem. Nothing to do with craps whatsoever, despite the originating thread author’s assertion, but classic nonetheless.


stopete July 29, 2003 at 11:23 pm

I am in the process of installin MT on a windows 2000 server, Apache, and using Mysql as my DBM. However I am running into a problem that I think you did too, When I run mt.cgi on the browser it doesn’t recognize DBD-mysql being install. However, in the DOS Shell it tells me I have it. Help if you can.


john July 30, 2003 at 8:05 am

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