?-Dave_Mysterious-?12 Jul 2004

I would have thought it didn't matter, but that is the obvious answer and so probably not it.

Maybe it is switch, because whatever door you choose there is always an empty one that can be shown to you, so the probability you have chosen the right door is still 1/3 after door B is revealed, so the probability the prize is in the remaining door is 2/3.

I mean, you either have chosen the right door initially (proability 1/3) or you haven't (probability 2/3). opening door B doesn't change anything, because whatever door you open, there is always an empty door that the host can reveal. It doesn't really tell you anything.

But it would seem a bit odd that you could have two doors, one of which contains a prize, and you have no information as to which it is, and the probability (as far as you are concerned) is not 50:50.