This chapter is about “The Monty Hall Problem”. In a magazine called Parade is a column called “Ask Marilyn”. Marilyn vos Savant write this and you can send in mathematic questions for Marilyn. She is honored by “The Guinness Book of World Records” for the human with the highest IQ. A reader askes Marilyn, what he should do, when he is in a TV show and he has to pick from one of three doors. Behind two of the three doors there are goats and behind one door there is a car. After he picked, the show master gives him a chance to change his mind. The question is: Should he change his mind or not?
She answers, that you should change your mind, because then you have a 2/3 chance that you win. Many mathematicians all over US send in, why she was wrong. In that time 92% of all letters she got, are about that she is wrong. Someone says, if all the Professors and Doctors would be wrong, that said she is wrong, the country would be in very serious trouble.
But she is right. You can explain that easy by listing all the possible outcomes: If you pick one of the two wrong doors and you change your mind, you get the car. So there are two possible ways of getting the car already, if you change your mind. You only don’t win when you pick the right door and change your mind. But there are two doors with a goat and only one door with the car, so you have a 2/3 possibility to win a car.