Chapter 16. Building Incremental Knowledge

Marilyn vos Savant is a U.S. columnist and author who is well known for her column in PARADE magazine answering interesting, mostly mathematical, questions. Her most famous column in 1990 provided an answer to the "Monty Hall problem" (named after the well-known host of Let's Make a Deal ). The letter positioned the reader as being a game-show contestant given the choice of three doors:

Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?"

Should you change your choice of door? Before thinking about the answer to the question, it is important to add one point of clarification to the game-show question. The host knows which door the car is behind and to prolong the show's tension will always open a door with a goat behind it.

Marilyn vos Savant opened Pandora's box when she argued you should switch as you have a one-in-three chance with your first choice (door one), but a two-in-three chance if you change to door two. When this question and answer was published, it is reputed to have generated more controversy than almost any other topic in the magazine's history. Readers didn't just disagree with the answer; they were outraged! Before looking to why there was such a negative response to the answer, it is important to ensure that readers understand why vos Savant was ...

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