[dba-Tech] The Three Doors Problem

John

 >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.

You can test your theory empirically. Visit 
http://people.hofstra.edu/staff/steven_r_costenoble/MontyHall/MontyHall.html. 
Do a dozen trials of holding your choice, and a dozen of switching it. 
Kep a count of the number of wins with each strategy. That gives you a 
2x2 table. Now visit http://www.unc.edu/~preacher/fisher/fisher.htm, 
plug in your numbers in the little table near the bottom, and click 
'Calculate'. The 'this tail' number is the probability that your numbers 
could have come about by chance from a scenario where the probabilities 
were 50-50.

Or if you prefer, you can keep your theory :-) .

PB

-----

John W. Colby wrote:

>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 :-)
>
>
>
>
>
>
>  
>
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