The Monty Hall Problem

The Setup

1. Three doors. Behind one: a car. Behind the other two: goats.
2. You pick a door.
3. The host (who knows where the car is) opens a different door to reveal a goat.
4. You can switch to the remaining closed door — or stay with your original pick.
5. Should you switch?

In 1990, Marilyn vos Savant published the correct answer in Parade Magazine. Over 10,000 people wrote in to say she was wrong — including hundreds with PhDs. Paul Erdos, one of the greatest mathematicians of the 20th century, refused to believe it until he ran a simulation. Play enough rounds below and the 2/3 vs 1/3 split will emerge from your own choices.