You are the contestant in Let's Make A Deal. Monty Hall offers you a choice of 3 doors. You choose one. Then Monty opens one of the other two, behind which there is always nothing. He then offers you the chance to keep your door, or trade it for the remaining door. Should you keep or trade, or does it matter?
Warning: According to Marilyn Vos Savant, who posed this problem in Parade magazine a few years ago, she received quite a bit of personal insults, including some from PhD mathematicians, after she published the answer. I don't know how many ever apologized, but suffice it to say, this problem has the potential to embarrass anyone. Originally, though the answer seemed obvious to me, I got it wrong, and I didn't believe the right answer until I wrote a little computer program to run umpteen trials. I thought about it again, and suddenly the right answer became the obvious one.
Statistics don't lie. But sometimes the people who use them do. |
