Stick or Switch?

A classic American sixties game show, hosted by Monty Hall, involved contestants choosing one of three doors. Behind one of the doors was a valuable  prize such as a new car. Behind the other two doors was something relatively worthless like a banana. After the contestant chooses one of the three doors Monty Hall (who knows which door has the prize behind it) always reveals a door (other than the one chosen) that has a worthless item behind it. He now poses the question to the contestant:

"Do you want to switch doors or stick to your orginal choice?"

Most people assume that there is no benefit in switching, i.e. that by sticking to their orginal choice they have a 50% chance of winning. 
Click here for an explanation of why they are wrong.

Norman Fenton

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