>Walter,
>
>Al (and others) are right, it makes no difference if you change your guess. Deciding NOT to change doors is also a choice, therefore your chance is always 1/x where x is the number of remaining doors. When Monty Hall opens one of the wrong doors, 'x' is reduced by one. When he gives you a chance to choose again, your chances are 1/x whether you change your guess or not. Changing does not improve your chances.
>
>Note to Dan Cummings: the name of the show was Let's Make a Deal.
>
Rick,

This is not correct and it has been proven with empirical testing. The issue of confusion is the removal of one door. At first you have a 2/3 chance of selecting the wrong door, odds are you will be wrong. After one of the wrong doors is opened then there are two doors left, the one you chose with 2/3 chance of being wrong and the other with a 1/2 chance of being right. If multiply the two probilities you get 1/3 chance of the other door being correct or wrong while there was still a 2/3 chance that the first choice was wrong and only a 1/3 chnace it was right.

The mathematics say that over an extended series of tests the other door will more often be the correct one.

The first time I heard this puzzle I was a non-believer too. Then I was shown the math and the emperical tests that proved the math was right.