[dba-Tech] The Three Doors Problem

LOL, but the answer is screwy.  Now take the example where TWO people are
choosing doors simultaneously.  The third door is shown to NOT contain the
prize.  Both people should swap by the logic of the puzzle, but one of them
is still going to lose and the other win.  Each person (door) has a 50%
probability of winning.  Which one will win?  There is no way to predict the
answer, each person has a 50% probability of winning the prize.

The logic SOUNDS good but is screwy.  Each door has a 1 in 3 chance of being
a winner.  Eliminate one door and each door has a 1 in 2 chance of being a
winner.  It matters not whether the third door is eliminated during the game
or before the game starts.

And Arthur, while your door just increased from 1 in 3 to 1 in 2, so did the
other door.  It matters not whether you switch or whether you stay, you have
a 50/50 chance of winning.  There is no particular reason to switch, but you
don't affect your odds in the slightest by switching.  Pick a door (of the
two remaining), any door, and you have a 50/50 chance.

John W. Colby
www.ColbyConsulting.com 

Contribute your unused CPU cycles to a good cause:
http://folding.stanford.edu/

-----Original Message-----
From: dba-tech-bounces at databaseadvisors.com
[mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of Stuart McLachlan
Sent: Thursday, August 25, 2005 10:20 PM
To: Discussion of Hardware and Software issues
Subject: Re: [dba-Tech] The Three Doors Problem


On 25 Aug 2005 at 20:04, Arthur Fuller wrote:

> I am the host of a TV program and you are the guest. This is the deal: 
> there are 3 doors. Behind one of them is $100 million. Behind the 
> other two are a dead catfish and a dead pickerel respectively. I 
> invite you to select a door. You choose any one of the three: call it 
> x I open another door, and say, Had you selected door y, you would 
> have won a dead catfish. Now, would you like to stick with your 
> original choice or switch to the other door? Does it matter? If not, 
> why not? If so, why so? There is a clear answer to this problem. Who 
> is going to be the first to come up with it? Arthur
> 
> 

Ah, the good old Monty Hall puzzle.

Strictly speaking, you need to qualify it by saying "I open another door 
which I know contains a dead fish and show you the contents"  If you could 
open the money door by accident, it is a different situation.

Anyhoo, the answers is:
Yes it matters, you should swap.  

I won't give the reason now  'cause it's a spoiler.   I know some peole 
will not agree with me and will go to great lengths to explain why I am 
wrong :-)






-- 
Stuart


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