The Monty Haul Question, Revisited

Dogblog got a really good explanation, apparently from Dean Esmay, who first posted the puzzle:

Say you plan to change doors.

2/3 of the time, your first pick is wrong. When that happens, Monty HAS to show you the right door, as there is only one empty door for him to open, he opens it, and you choose the other door, which will necessarily have the prize.

1/3 of the time, your first pick is right, you change doors, and you're screwed.
So 2/3 of the time, you win.

I think that's pretty convincing.

And This Is Even More Elegant Update: "Right" offers...

Assume you choose door A.

Monty reveals nothing and offers to let you trade for BOTH B AND C.

This is essentially the same as the original question.

Revealing the empty door won't change it.

That's a good way to put it. Forget about the "opening wrong doors" show-biz.

posted by Ace at 08:51 PM

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