Jane Street Online Assessment
Jane Street's screen is built around probability, expected value, and mental math, not algorithmic coding. The first-round assessment is a short set of brain-teasers where your reasoning matters as much as the number; a separate quant-research round adds a live coding exercise, and trading-operations roles get an Excel-based task.
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Trading & Research — Trader / QT / Research
A short, timed set of probability, expected-value, and mental-math questions (prime-sum parity, an optional-reroll dice game, a Bayesian coin re-flip, a two-urn posterior bet, plus counting and estimation). You explain your reasoning, not just the answer.
- Even Sum When Drawing 4 of the First 8 Primes Probability · easy
- Ten-Sided Die: Stop or Reroll Without Busting Past 10 Probability · medium
- Three Biased Coins: Probability the Reflip Is Heads Again Probability · medium
Trading & Research — Quant Research coding round
A second-round live coding exercise for quant-research candidates - a clean implementation problem (not LeetCode trickery), with follow-ups on efficiency and on shaping the code into a reusable library.
- Gravity Grid k-in-a-Row Coding · hard
What the Jane Street online assessment screen looks like
Candidates describe the Jane Street online assessment as a written or HackerRank-hosted set of about 4 questions in 30 minutes for the Trader, Quant Trader and Research tracks. The questions are probability, expected value and mental math (a prime-sum parity count, an optional-reroll dice game, a Bayesian coin re-flip, a two-urn posterior bet, plus counting and estimation), and you are asked to explain your reasoning, not just type the number. There is no algorithmic coding on the first-round screen: the quant-research track adds a separate live coding round, and trading-operations roles get an Excel-based task instead. Our timed replica runs 8 questions in 30 minutes; the first four follow the recurring Trader / QT template and the rest are the mental-math questions, answered as a reduced fraction or a decimal.
How to prepare for the Jane Street online assessment
Work the reported question families above with a full solution each, then take the timed replica so the 30-minute pace is automatic. Because the screen asks for your reasoning, practise writing a two-line justification for every answer rather than only the value. Three families carry the screen: expected value of small games, Bayesian updates on coins and urns, and fast counting; the topic hubs below cover each with worked solutions. For the puzzle-style thinking Jane Street is known for, the puzzles guide is the natural complement, and the interview-process page shows what follows a pass.
Probability interview questions →
Expectation interview questions →
Bayes theorem interview guide →
Mental math for trading interviews →
Jane Street OA — FAQ
What is the Jane Street online assessment?
Jane Street's screen is built around probability, expected value, and mental math, not algorithmic coding. The first-round assessment is a short set of brain-teasers where your reasoning matters as much as the number; a separate quant-research round adds a live coding exercise, and trading-operations roles get an Excel-based task.
What is the format of the Jane Street OA?
It runs as 2 tracks (Trader / QT / Research, Quant Research coding round). Trading & Research, Trading & Research, each timed and auto-graded where applicable.
How do I practice for the Jane Street online assessment?
Work the sample questions above (each with a full worked solution), then take the interactive Jane Street OA practice on QuantVault. For the full interview, see the Jane Street interview-questions set.
Is the Jane Street online assessment on HackerRank?
Candidate reports describe the first-round screen as written or HackerRank-hosted: about 4 probability, expected-value and mental-math questions in 30 minutes, where you explain your reasoning as well as the answer. It is not a HackerRank coding test. The quant-research coding exercise is a separate live round, not part of the online assessment.
How long is the Jane Street online assessment?
About 30 minutes for roughly 4 questions on the Trader, Quant Trader and Research tracks, per candidate reports spanning 2017 to 2025. Our replica runs 8 questions in the same 30 minutes, so its pace is slightly tighter than the reported screen.
What questions are on the Jane Street online assessment?
The reported set is probability, expected value and mental math: a prime-sum parity count, an optional-reroll dice game where you decide whether to stop or reroll without busting, a Bayesian coin re-flip, a two-urn posterior bet, and counting and estimation items. Each of the sample questions on this page is one of those families with a full worked solution.
Is there coding on the Jane Street OA?
Not on the first-round screen, which is built around probability and mental math rather than algorithmic coding. Quant-research candidates get a second-round live coding exercise: a clean implementation problem with follow-ups on efficiency and on shaping the code into a reusable library. Trading-operations roles get an Excel-based task.