Probability and market-making interviews are among the most distinctive rounds in quant trading. They are heavy on probability and expected value, light on finance trivia, and unusually focused on how you think rather than whether you reach the answer.
The process at a glance
A representative process runs from phone screens to an in-person final stage. The final round mixes several question types:
| Area | What it looks like |
|---|---|
| Probability & statistics | Dice, coins, cards; "what's the fair price of this game?" |
| Expected value | Pricing bets and decisions under uncertainty |
| Mental math | Quick, accurate arithmetic woven into larger problems |
| Market-making games | Quote a price on an uncertain quantity, update as info arrives |
| Coding & data analysis | For technology and research roles, in your strongest language |
Key insight. Desks running this format generally do not test knowledge of finance or economics - Jane Street, for instance, states publicly that a finance background is optional for trading and that it does not test finance knowledge. What is being sampled is your reasoning, not your vocabulary.
What they're really evaluating
The recurring theme in publicly available descriptions of this format is that the method matters as much as the answer. Interviews are collaborative: they want to see you reason out loud, take a hint gracefully, and work the problem with the interviewer.
Worked example: the spirit of it. Asked to price a simple card-drawing game, a strong candidate narrates the expected-value setup, states assumptions, sanity-checks the number, then adjusts when the interviewer adds a twist. A silent, exact answer often scores worse than a clear, slightly-off one - because the job is collaborative problem-solving, and that is exactly what they are sampling.
How to prepare
- Build deep probability and expected-value fluency - the highest-leverage prep by far.
- Practise quoting and updating prices. The Make a Market and Take the Bet games train exactly this under time pressure.
- Rehearse thinking aloud, so your reasoning is legible to an interviewer.
- For technical roles, be ready to code cleanly in your strongest language.
When you are ready, work the question set for this format and run the timed Probability OA to simulate the pace. For neighbouring formats, see the EV and betting games and timed speed assessment guides.