The Monty Hall problem

I found a rather interesting article, called the Monty Hall problem on Wikipedia.

A thoroughly honest game-show host has placed a car behind one of three doors. There is a goat behind each of the other doors. You have no prior knowledge that allows you to distinguish among the doors. "First you point toward a door," he says. "Then I'll open one of the other doors to reveal a goat. After I've shown you the goat, you make your final choice whether to stick with your initial choice of doors, or to switch to the remaining door. You win whatever is behind the door."

You begin by pointing to door number 1. The host shows you that door number 3 has a goat.

Now, do your odds of getting the car increase by switching to door number 2?

As it happens, the answer is "yes", since switching gives you a 2 in 3 chance of winning instead of the intuitively assumed 1 in 2 chance.

Wikipedia describes the full details about the paradox and the Mozy Blog provides a nice, interactive demonstration based on playing cards (ace and jokers) instead of car and goats.