40 questions reported in Jane Street interviews, organised by the group that asks them. Every question carries a model answer and graded feedback on your own attempt.
Questions
Easy · Medium
Hard
Model builds
Built in the spreadsheet grid
Currently advertised programmes.
Expected value under pressure, adverse selection and inventory risk. 17 questions
A basic mental-maths screen that tests whether a candidate separates probability from payoff.
You pay $3 to play a game. A fair six-sided die is rolled: you receive $12 on a 6 and nothing otherwise. Should you play once? What would change if you could play 1,000 independent times?
A basic prop-trading exercise tests whether candidates translate probabilities into a price and a trading decision.
A contract pays $100 if a coin lands heads and $0 if it lands tails. You believe heads has a 55% probability. What is the fair value? Would you buy at $54, and would you sell at $56?
A first-round market-microstructure check for candidates new to electronic trading.
A stock is quoted at $49.98 bid and $50.02 offer. You want to buy 1,000 shares now. Explain the difference between sending a market order and a limit order at $50.00.
A first-round electronic-trading screen checks that a candidate can read a two-sided market precisely.
An ETF is quoted at $101.20 bid and $101.28 offer. What are the mid-price and bid-ask spread? If you buy 500 shares at the offer and immediately value them at the mid-price, what is your…
An execution-trading interview checks that a candidate can reconcile fills before offering an opinion on execution quality.
You buy 1,000 shares in three fills: 200 at $24.90, 500 at $25.00 and 300 at $25.10. What is your VWAP? If the arrival mid-price was $24.95, what was your implementation shortfall in dollars before…
Fermi estimation is a standard prop trading round. You have sixty seconds.
How many tennis balls fit in a Boeing 747? You have one minute.
A prop-trading technical round checks whether you can construct a hedge from payoffs rather than memorise Greeks.
A stock is $100 today. Tomorrow it will be either $120 or $90. A call with a $100 strike pays $20 in the up state and $0 in the down state. How many shares hedge one short call in this one-period…
A sizing follow-up tests whether you distinguish an estimated edge from a known probability.
A trade wins 55% of the time and loses 45% of the time. It makes or loses 1% of the capital allocated. What is full Kelly sizing, and why might a trading desk use less?
The interactive trading game used at every prop firm.
I have a bag with 10 balls, each numbered 1 to 10. I draw three and the contract settles on their sum. Make me a market. Then I show you that one of the balls drawn is a 10, what's your new market?
Options market making interviews probe what you do when you cannot hedge continuously.
You're short gamma into the close, with earnings after the bell. What are your options, and what do you do?
A senior prop-trading case tests how you turn fill data into a controlled quoting decision.
Your ETF market-making strategy earns the spread on most fills, but over the past week your fills lose 4 basis points on average after one second. Volatility and displayed spreads are unchanged. What…
The practical hedging problem on any desk that cannot trade the exact instrument.
You're long $10m of an illiquid corporate bond and want to hedge the rates risk. The only liquid instrument is a Treasury future. What ratio do you use, and what risk remains?
Electronic market making interviews test whether you understand the microstructure you'd trade in.
Why does latency matter to a market maker, and what is queue position worth?
Tests whether you reason about why a bet is being offered, not just its expected value.
I offer you a bet: I roll a fair die, and if it comes up 6 I pay you $10; otherwise you pay me $1. Do you take it? How much would you pay for the right to play 100 times?
The core mechanic of market making, tested with a live scenario.
You're making a market at 99 / 101 in a contract. You get hit on the bid three times in a row and are now long 300 lots. What do you do with your quote?
Trading firms use this to test whether you understand compounding and ruin.
You have an edge: a bet that pays 2:1 and wins 40% of the time. What fraction of your capital should you bet, and why not more?
A systematic-trading review after a research backtest appears to generate alpha around splits, special dividends and index changes.
A daily equity signal shows a sharp return improvement after a new corporate-action vendor feed is added. The gain is concentrated around special dividends, rights issues and spin-offs. How would you…
Multiple testing, out-of-sample discipline, capacity and decay. 8 questions
Asked to see whether you can explain a counterintuitive result clearly under pressure.
Three doors: one hides a car, two hide goats. You pick door 1. The host. Who knows what's behind each door. Opens door 3 revealing a goat, then offers you the chance to switch to door 2. Should you…
Tests recursive reasoning. A staple at trading firms.
You roll a fair six-sided die. You may either take the value shown in dollars, or re-roll. You get at most two rolls total. What is the expected value of the game if you play optimally? Then: what if…
A Bayesian question testing whether you anchor on the prior or the evidence.
A test for a condition affecting 1 in 1,000 people is 99% accurate. 99% true positive rate and 99% true negative rate. Someone tests positive. What is the probability they have the condition?
Tests whether you can approximate rather than recall.
In a room of 23 people, what is the probability at least two share a birthday? Explain your reasoning and why the answer surprises people.
A classic Bayesian warm-up at quant trading firms.
You have two coins. One is fair; the other lands heads 75% of the time. You pick one at random and flip it 3 times, getting heads every time. What is the probability you picked the biased coin?
Systematic trading interviews use this to test whether you can reason about strategy economics.
A strategy makes 250 trades a year, wins 55% of the time, and wins and losses are the same size (1 unit). Estimate the annual Sharpe ratio. What does this tell you about how much edge a systematic…
The signature exercise at proprietary trading firms.
Make me a market on the sum of the digits of a randomly chosen phone number in the room. Then I'll trade against you. Explain how you'd think through the whole exercise.
A recurring structure in quant interviews. Set up the recursion, don't simulate.
You start at position 0. Each step you move +1 with probability 0.5 and −1 with probability 0.5. What is the expected number of steps to first reach +3? Then: what changes if the walk is bounded below…
Market impact, liquidity provision, borrow and event flow. 6 questions
Common in execution services, and in any conversation about market structure.
A client needs to sell 2 million shares of a stock that trades 500,000 shares a day. Walk me through how you'd approach the execution and the trade-offs involved.
Central to any market-making interview at a prop firm or bank.
You're making a market in a stock. What determines the width of your bid-ask spread? A large institutional client asks for a two-way price in size. How does that change your quote?
An offer-ready equities-volatility case that tests event-risk arithmetic, distribution thinking and disciplined trade selection.
A $100 stock reports earnings tomorrow. The at-the-money straddle costs $8, implying an approximately 8% move, while the stock's last eight earnings moves were 3%, 4%, 5%, 6%, 7%, 9%, 12% and 15%.…
Asked at market makers and any desk touching ETF flow.
How does an ETF stay close to its net asset value? What happens when it doesn't?
A market-structure case for an equities trader responsible for risk when displayed liquidity vanishes during a fast market.
You are long 300,000 shares of a $30 stock after a client block. Mid-session, news hits and the stock falls 9% in seconds, triggering a volatility halt. Before the reopening auction, the indicative…
An offer-ready market-structure case for desks that execute index flow and closing-auction risk.
A stock is being added to a major market-cap-weighted index at the close. Passive funds tracking the index must buy an estimated 8% of average daily volume. How would you expect the stock and its…
Greeks, skew, hedging costs and payoff construction. 5 questions
A desk arithmetic check after a candidate explains delta conceptually.
A dealer has sold 100 call-option contracts. Each contract covers 100 shares and each call has a delta of 0.60. How many shares should the dealer buy or sell to be delta neutral? If the stock rises…
Trading interviews use this to test whether you can construct an arbitrage on the spot.
State put-call parity. A stock trades at $100. The $100 strike call trades at $8, the put at $5, and the risk-free rate is 4% with 1 year to expiry, no dividends. Is there an arbitrage? If so,…
Standard for derivatives desks and quant trading interviews.
Name the inputs to the Black-Scholes model and the direction each moves a call option's price. Which input is not observable, and what does that imply?
Market-making interviews will push hard on gamma.
Define delta and gamma. You are short a straddle and delta-hedged. Explain what happens to your position as the underlying moves, and what you're actually long or short.
Volatility desks ask this to see whether you understand the market, not the model.
Equity index options show higher implied volatility for downside strikes than upside. Explain why the skew exists and what it tells you about the market's assumptions.
Stochastic calculus, VaR and expected shortfall, and model limitations. 3 questions
Mental math screen. Expect several of these in rapid succession, no calculator.
An investment compounds at 9% annually. (a) Roughly how long to double? (b) What is it worth after 24 years, as a multiple? (c) A fund returns 2.5x over 6 years. What is the approximate annualised…
Quant research and derivatives interviews test conceptual understanding over derivation.
Why do we model stock prices as geometric Brownian motion rather than arithmetic Brownian motion? What does Itô's lemma tell us, and why is the drift of log returns lower than the drift of prices?
A derivatives-risk interview uses this to test whether you recognise nonlinear exposures before discussing a VaR number.
A book is delta-neutral at the start of the day. Why can it still lose heavily after a large market move? Explain the role of gamma, volatility and hedging liquidity.
Duration, curve trades, auctions, basis and central bank reaction. 1 question
A staple opener in sales & trading and macro interviews.
Explain what the yield curve is and what an inversion means. Why has inversion historically preceded recessions, and what are the limits of that signal?
Write your answer, get it graded on technical accuracy, completeness and communication, and see exactly which mechanic you missed.
Company tags reflect where a question type is commonly reported in interviews. They are not sourced from, endorsed by, or affiliated with Jane Street.