QUESTION 1 / 20 · BASICSEasy
You roll a fair die. What's the probability of an even number?
THE MONTY HALL PROBLEM
Stick or switch?
A car is behind one of three doors. You pick one. The host, who knows where the car is, opens another door to show a goat, then offers you the chance to switch. When this was published in 1990, thousands of readers, including many mathematicians, insisted the answer was wrong.
Pick a door.STEP 1 OF 2
YOUR RESULTS SO FAR
Sticking–0 wins in 0 games
Switching–0 wins in 0 games
What this probability test covers, in short
Twenty multiple-choice questions at upper-secondary to first-year university level, four on each of five topics: basic probability, counting, conditional probability and Bayes, distributions, and expected value. Several are classic puzzles where intuition misleads.
Dice and coins are fair unless stated. The test is our own and not normed.
By What's Your IQ · Reviewed 5 Oct 2026- Format
- 20 multiple-choice questions
- Level
- A-level / AP to first-year university
- Bonus
- Monty Hall game and 1,000-game simulator
- Founded
- Pascal and Fermat's letters on gambling, 1654