Monty Hall Odds Explained :

[Kramer]

http://en.wikipedia.org/wiki/Monty_Hall_problem

[Gobbler's Knob]

Wikipedia will be the end of us all, it's more evil than google. Computers are the devils shop tools.

[Kramer]

prior post Gobbler,

posters didn't understand answer ...

Cognitive Illusions :

[The Judge]

Originally Posted by wikipedia

In some versions of the Monty Hall problem the host's behavior is not fully specified. For example, the version published in Parade in 1990 did not specifically state that the host would always open another door, or always offer a choice to switch, or even never open the door revealing the car. Without specifying these rules, the player does not have enough information to conclude switching will be successful two-thirds of the time.

This applies in the scenario originally presented by Kramer.

Imagine that I set up three boxes in front of you, and call them 'A', 'B', and 'C'. I've placed a twenty dollar bill inside one of the boxes.

I know which one has the $20, and you do not. I ask you to pick a box, any box. Let's agree for ease of discussion that you pick Box 'A'. Now, what are the odds that you selected the box with the money in it?

You, of course, answered one in three. So far, so good. Now, imagine that I do my best Monty Hall imitation and tell you that I'm going to give you a chance to change your guess, but first I'm going to open one of the boxes. Then, with much ceremony, I proceed to show you that - AHA! -

there's nothing inside of Box 'C'.