This question is about an old TV game show (I think…). There is a prize behind one of 3 doors. You choose one door and then the host tells you which of the remaining 2 doors it is NOT behind. You then have the choice to keep your first choice or go ahead and switch to the other door. Statistically, is it better to switch or keep the first choice?
Do a search on this. Cecil has already answered it:
http://www.straightdope.com/classics/a3_189.html
Although this is one I think he wishes would go away. His answer seemed to have caused more back and forth debate than almost anything else he has published in the Straight Dope (at least as far as I have found).
It was again mentioned in this thread http://boards.straightdope.com/sdmb/showthread.php?threadid=25772 If you look 2/3 down you will see brad_d brought it up and I contradicted him and he turned out to be right. I think that is the most clear explanation I have seen. It does assume the host always opens a door though. It seems part of the semantics of the original post was about how often the host opens a door
Ah, the famous Let’s Make A Deal Puzzle :p. Various people, including the Car Talk brothers, Tom & Ray Magliozzi, have set up simple games to test this question. The results always come out that you are better off switching. I’ve played their game myself and can confirm that if you switch, you are twice as likely to win than if you don’t.