I built a small competition called Inference. Three problems, three weeks, no code required.

Each round I put up a question pulled from the kind of reasoning that shows up in trading, gambling, and statistics — parimutuel betting, market microstructure, derivatives pricing. You read the problem, work out an answer, write a short explanation, and submit. Once the round closes I score everyone and post a leaderboard.

Round 1 is about parimutuel horse racing. If you want a taste: parimutuel markets are interesting because your return depends not just on whether you pick the winner but on what everyone else bet. The house takes a cut, and the rest gets split among winning tickets in proportion to how much was wagered on each outcome. Estimating the true probabilities from the final pool — and figuring out when the market is mispriced — is the actual problem.

Rules worth knowing:

• Three submissions per round total. You can update your answer up to three times before the round closes. The latest one is what gets scored.
• Submissions need an answer in the format the problem asks for and at least 50 characters of reasoning.
• Talking through problems with friends is fine. Submitting the same answer and reasoning as someone else is not.
• LLMs are allowed but discouraged. The point is to learn something.
• Ties break by earliest submission.

The whole thing runs on the honour system. Submit what you reckon is right, show your working, and try to learn something.

Have a go.