John W. Colby
jwcolby at colbyconsulting.com
Fri Aug 26 07:36:41 CDT 2005
In fact the problem CORRECTLY STATED is similar to blackjack, where knowing what came before affects the PROBABILITY of what will come next. 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: Friday, August 26, 2005 8:02 AM To: Discussion of Hardware and Software issues Subject: Re: [dba-Tech] The Three Doors Problem On 26 Aug 2005 at 13:40, Lembit Soobik wrote: > I think you make it too complicated. > forget the history. That's the flaw in your argument. You can't forget the history. > at the end, what you have is two doors: > one is the winning door > just pick one. > doesnt matter what you had picked before Yes it does. > doesnt matter whether you swap or not. Yes it does. > and you can write simulation programs till the cows come home And if they are written correctly, they will give you the correct answer over enough trials. > fact is you have one right and one wrong and have to pick one so you > have 1 out of two chance thats all. > Fact is, when you first picked you had three choices. The odds are 1/3 you are right initially. In that one case, switching is wrong. In the 2/3 where you were wrong initially, changing will always give you the correct door. (Assuming the problem is stated correctly. As I said previous, 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.) So in 1/3 cases you win by staying, in 2/3 cases you win by switching. -- Stuart _______________________________________________ dba-Tech mailing list dba-Tech at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/dba-tech Website: http://www.databaseadvisors.com