Marilyn gives the correct solution to a simple but tricky problem. She is viciously attacked by an army of highly-placed academics who insist that she is wrong. She holds her ground. They finally admit their error and are repentant.There has been some discussion about whether or not Monty always offered the switch and if his doing so depended on whether the contestant chose the right door to begin with. Monty said that he did not always offer the switch. Sometimes he would offer it to lure the contestant away from the right door, and to keep the audience off balance sometimes he would bluff and offer the switch when the contestant had chosen wrongly to see if he could make him be stubborn. If we knew the probability that Monty would offer the switch as a function of the accuracy of the contestant's choice we could use it in deciding the best strategy. That is the approach we would take in attempting to crack the game commercially. In presenting it as a puzzle, however, it is customary to assume that Monty always offers the switch regardless. Decide on your strategy and turn the page when you are ready.Monty Hall is the MC of a television quiz show called Let's Make A Deal. One of the games he offers uses three doors. Behind one door is an expensive automobile and behind each of the others is a goat. Nobody but Monty and the stage crew know which door leads to the automobile. The essence of the game is that the contestant is permitted to choose one of the three doors. If he chooses the right door he wins the automobile. If he chooses a wrong one he gets goat cheese. There is a twist. After the contestant has chosen a door Monty asks him if he wants to change his mind. To help him, or perhaps to confuse him, he opens one of the doors not chosen and shows that it conceals one of the goats. The question is, should you stick with the door you chose originally or should you accept the switch offered by Monty, and what is the probability of winning the automobile in each case?