The applet below simulates the Monty Hall problem. In one form of the problem, there are three doors, two of which have goats behind them, and one of which has a million dollars behind it. You choose one of the doors, and then Monty opens one of the other doors, revealing a goat. He then asks if you want to switch to the remaining door. This applet simulates the number of wins you will have if you switch, or if you don't switch.

In another form of the problem, Monty chooses between the remaining doors randomly. If he opens the door with a million dollars, you lose. If he picks a goat, you can then either switch your door or not. You can choose which form of the game to simulate by using the second group of radio buttons.

Additionally, you can see what happens in each game by selecting the checkbox.