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HOW SURE ARE YOU?

Probability Lab

Not just yes or no. Put a probability on it.

2 min · FREE

Play Probability Lab

A bag contains ten tokens. Set the chance of drawing an orange token, then reveal one simulated draw. Five rounds. The Brier score averages squared probability errors; lower is better. A short run is noisy, not proof of skill.

No sign-up. No deposit. No cash prizes.

How to play Probability Lab

A bag contains ten tokens. Set the chance of drawing an orange token, then reveal one simulated draw. Five rounds. The Brier score averages squared probability errors; lower is better. A short run is noisy, not proof of skill.

Understanding the practice score

The bag contains ten tokens. Choose a probability before revealing one simulated draw and repeat for five rounds. The Brier score averages squared differences between your probabilities and the outcomes; lower is better. A short run can be noisy and does not prove forecasting skill.

Free play and replay

No account, download, purchase or deposit is required. The same game, date and content version reproduce the same challenge. Replays are labelled separately from a first attempt in the retained local history. Scores are local, not verified leaderboard results. There are no cash prizes.