Yes he should switch, and I’m not seeing how this is different than the original problem.
The surviving contestant had a 1 in 7 chance of being correct with his first pick. Five wrong answers were then revealed, and a choice given: Stick with your 1 in 7 guess, or switch to “the field,” which has a 6 in 7 chance of being a winner.
I’d have an answer if it weren’t for this. Some other possibilities:There are five other colors it could be. Some guy named Mark is involved. He’s apparently quite charming.And my (non)answer: Quarks. They can be yellow (or antiblue), as well as strange. They can apparently be wooden. And the dairy product quark is sometimes called “dry cottage cheese.”
As I see it, there are two possible cases where this happens to me:
2/7 of the time, I’ve got the winning door, and Monty has no choice but to present me with this decision.
3/7 of the time, Monty has the winning door, and Monty chooses me at random, i.e., 50% of the time, or 3/14 of the time.
So 2/7 (or 4/14) of the time, my remaining door is the winning door. 3/14 of the time, Monty has the winning door.
I stick with my original choice for a slight advantage.
I say you switch!Although the car might be behind each door with equal probability, a contestant that makes it to the final round could not be there in two out of the seven universes: the ones where the opponent chose a door with a car. So there are only five possibilities to analyze. Since (as with the original MH problem) opening a door with a goat among a set of N doors doesn’t change the total probability that the car is behind one of those doors, the odds that the car is behind his remaining chosen door is 2/5, and 3/5 that it’s behind Monty’s remaining door. Therefore he should switch.
I typed out a long explanation, but got to the end and found myself with a 50/50 chance, which I’m almsot certain means I screwed up.
The thing that I think you’re missing is that in 3 of those five possibilities, there was an equal chance it went to your opponent; two of those five possibilities meant that it had to go to you in this final round, meaning these two possibilities should be weighted double.
Last time, someone designed a program to test it. Assuming Monty always sends someone to the final round and eliminates someone, surely this could be modeled. I predict that sticking with your choice gives a 4 in 7 chance of success, given ten thousand trials.
Yep, I realized this after I posted it. You’re absolutely right, and means I need to look at 14 universes, not 7. Doing that, I get the same answer you did.
I’ve used dry mustard and yellow mustard plenty of times. Can’t recall having used wooden mustard before, though. I suppose there is some strange mustard out there.
Is mittu still around? He didn’t put you up to this, did he?
You know, Chronos, your profession really gives you away here. It was among the first things I thought of, but I really had a problem with “dry” and “wooden”. Then I happened to remember coming across an article about a new support system for houses. A little Googling confirmed my memory. After that, “dry” fell quickly as well.
I think someone else already guessed that, and while those can certainly be strange, and you could kind of sort of argue that they could be yellow, I’ve never heard of them being wooden or dry before this thread. And certainly they’re not always one of those things.
In other words, no, that’s not it. Would you like another hint? Perhaps, what sort of book you’d look in to find the answer?