Make a market

Market making questions are a staple of trading interviews: "make me a market on the sum of three dice". You need the expected value fast, and a quote that's tight without being wrong. This game drills exactly that, against the clock, with a rating that adapts to you.

How it works

1. Each round names a contract, like the sum of four dice or the number of flips until HHH. It settles at its fair value: its expected value.
2. Type a bid and an ask. If fair value is outside your quote, a trader picks you off and you score nothing.
3. With fair value inside, tighter is better: a tight market scores 10 points, a good one 5.
4. You have 90 seconds. Rated runs adapt: harder contracts and tighter markets as your rating rises.

Every fair value comes from the contract's exact probability distribution, not an estimate, so the feedback after each quote is exact. At the end you see every contract, your market and its fair value side by side.

Play make a market

Play with friends or a club

Challenge a friend with a duel link, or run a tournament for a club or class: one link, the same rounds for everyone, one run each, and a live leaderboard.

Also try Guess the correlation, or the probability puzzles.