GuestLighter --

Howard and I do not fundamentally disagree.

He said, "I was assuming that one of the doors still conceals the car," in asserting the second person's chances were 1 in 2

Where we differed: I assumed that the new person was getting to choose from what was left by the original contestant, and that his choice was influenced by that action. You and Howard, it turns out, assumed that the contestant had lost the game, leaving the car in play--but you did not clearly make that a part of the proposition.

The paragraph I wrote following my analysis reflects the problem you meant to describe. "Now you can change the game further by only having a second player if the first contestant fails to win the car. The new person facing two doors with the assurance there is a car available, and no other information, does have a 50/50 chance."

So, while I analyzed the problem as it seemed you were posting it, I also took into account the problem you say you were posing. On that, the three of us agree. I'm not sure whether we agree on my analysis when there is no car to be had for the second person.