PRACTICE GUIDE JANE STREET
Jane Street Strategy and Product Practice Test
The Jane Street strategy and product screen is 20 questions in 60 minutes - about 3 minutes each - answered by picking one of the options. There is no negative marking, so leaving an item blank gains you nothing over guessing.
Where it sits: Strategy and product screen. The practice sitting on this page runs the same item count, the same clock and the same marking rule, with questions generated by Outcry rather than taken from Jane Street.
Candidates consistently report probability and expected-value questions dominating the phone screens. Mental math helps, but the setup and reasoning are what get graded.
Outcry is not affiliated with Jane Street and has no access to their assessment content. This guide describes an assessment format that candidates report publicly; the questions here are generated by Outcry and are not Jane Street’s own.
What it screens
A quantitative trading firm active across equities, ETFs, bonds, options and currencies, known for OCaml and a strong internship pipeline.
- ✓Expected value computed fast and used to make a decision
- ✓Conditional probability and Bayes updates without formal notation
- ✓Ranking likelihoods rather than computing them exactly
- ✓Fermi estimation: decomposing an impossible question into three easy ones
Where it sits at Jane Street
This is the whole sitting rather than one section of it: 20 items in 60 minutes, on one clock.
There is no going back. You answer or skip, and the next item loads, which means the decision to leave an item is final at the moment you make it.
The format
These are the numbers the Jane Street sitting on this site runs on, matching the format candidates report.
| Questions | 20 |
|---|---|
| Time | 60 minutes |
| Per question | 3 minutes |
| Negative marking | No |
| Answer style | Multiple choice |
| Where it sits | Strategy and product screen |
What it tests, with a worked example
Every example below is generated by Outcry, drawn from the same question generators the timed drills run. None of them is Jane Street’s.
Expected value and odds
Pricing a bet, converting between odds and probabilities, and deciding whether to take it.
Example
A ticket costs 10. It pays 100 with probability 25%, else nothing. Expected profit?
- 25
- 15
- 90
- 5
Answer 15
25% × 100 = 25; minus the 10 cost gives 15.
Counting and combinatorics
Arrangements, selections and the complement trick that turns a hard count into an easy one.
Example
A counter sits on square 2 of a row numbered 0 to 12. Each tick it moves one square left or one square right with equal probability, and it stops on 0 or on 12. What is the probability it stops on 12?
- 5/6
- 1/7
- 1/6
- 1/2
Answer 1/6
The position itself is a martingale in a fair walk, so its expected stopping value equals its start: p x 12 + (1 - p) x 0 = 2, giving p = 2/12 = 1/6. Step size does not enter it.
Distributions you should know cold
Binomial, geometric and uniform means and variances, applied rather than quoted.
Example
Two fair dice are rolled. What is the chance the total is 8?
- 13.9%
- 41.7%
- 16.7%
- 23.8%
- 9.1%
Answer 13.9%
5 of the 36 ordered pairs total 8, so 5/36 = 13.9%. There are 11 totals and 21 unordered pairs, and neither set is equally likely.
Estimation under uncertainty
A number nobody knows exactly, reasoned to the right order of magnitude out loud.
Example
A balance reports which of two groups is heavier, or that they match. Exactly one bar in a batch is heavier than the rest. With 4 weighings and worst-case luck, what is the largest batch you can guarantee to pin down?
Answer 81
Counting outcomes: 4 weighings produce 3^4 = 81 distinguishable results, and each result can name at most one bar. The bound is met by thirds - weigh 27 against 27 and whichever way it falls you are left with 27 candidates and 3 weighings.
Ranking outcomes
Ordering several events by likelihood, where only the exact order scores.
Example
A non-dividend-paying share trades at $43.73 and the 9-month funding rate is 2.76% continuously compounded. The 9-month forward on 250 shares is quoted at $44.25. What is the trade?
- Buy the forward, short the shares and lend the proceeds: $98.66 at delivery
- Nothing, the difference between $44.25 and $43.73 is just the cost of carry
- Buy the forward, short the shares and lend the proceeds: $130.00 at delivery
- Buy the forward, short the shares and lend the proceeds: $96.64 at delivery
- Sell the forward, buy the shares with borrowed cash: $98.66 at delivery
Answer Buy the forward, short the shares and lend the proceeds: $98.66 at delivery
The fair forward is the spot carried to delivery: F = $43.73 x e^(0.0276 x 0.7500) = $43.73 x 1.020916 = $44.6446. The quote is $44.25, so the forward is cheap by $0.3946 a share. Buy the forward, short the stock at $43.73 and lend the proceeds: the deposit grows to $44.6446, the forward takes $44.25 of it, and the difference is kept. On 250 shares that is $98.66 at delivery. The gap between the forward and the SPOT, $0.52, is mostly carry and is not the edge. $96.64 is that edge discounted back to today, which is what it is worth now rather than at delivery.
Reading the question exactly
At least, exactly, and given that - the three phrases that change the answer entirely.
Example
A price rises 58% in one quarter and then falls 40% in the next. What is the net change over the two quarters?
- -5.2%
- 18%
- -23.2%
- -18%
Answer -5.2%
100 goes to 158, then loses 40% of 158, landing at 94.8. Net -5.2%. The naive answer 18% misses the cross term, which is -23.2%.
What a good score looks like
On a paper of 20 questions with no penalty for a wrong answer, the only thing an unanswered question can do is cost you. Probability rounds are usually marked as part of a wider battery, so a standalone threshold is rarely reported. Where candidates do describe one it clusters around getting two thirds of the items right, with the caveat that these sections are short enough that two mistakes move you a long way.
How to train for it
- 01Do them timed. A probability question you can solve in four minutes and the paper gives you ninety seconds for is a question you cannot solve.
- 02Sanity-check the magnitude before committing. A probability above one or an expectation outside the range of outcomes is a caught error, and these papers plant both as options.
- 03Work the complement first whenever the question says at least or at most. It is usually the shorter route and it is almost always the intended one.
TRAIN IT HERE
The drills that match each section
Likelihood Ranking
Order events from most to least likely - the exact screen-question format.
Fermi Estimation
Piano tuners in Chicago, atoms in a body - scored on order of magnitude.
Quitters Never Lose
A casino stopping-strategy game that is secretly a martingale lesson.
Tail Risk
Rare events and fat tails, and what they do to a plain expected-value estimate.
SIT THE FULL BATTERY
All the sections back to back on one clock, marked the way the real screen marks them, with a by-skill breakdown at the end. Included with any pass.
Also reported at Jane Street
Common questions
- Is the Jane Street strategy and product test multiple choice?
- Multiple choice. You pick one option per question.
- How long is the Jane Street strategy and product test?
- 20 questions in 60 minutes, which is about 3 minutes each.
- Is there negative marking on the Jane Street strategy and product test?
- No. A wrong answer costs nothing beyond the mark you would have earned, so leaving an item blank is never better than guessing at it.
- How do I practise for it free?
- Every drill linked on this page is free to play, with no account, inside a daily run cap. Questions are generated fresh each run, so there is nothing to memorise between attempts. The full Jane Street Strategy and Product Assessment sitting puts the sections back to back on one clock.
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