Quant internships at trading firms and hedge funds test quick, accurate thinking: probability, mental math, expected value and, for developer or research roles, coding. Many firms add online numerical tests or games early in the process. This page covers the rounds to expect, the questions that come up with what a strong answer contains, two sample answers, what interviewers expect from an intern, the mistakes that cost offers, and a two-week prep plan.
What the quant intern interview looks like
| Round | What happens | How to prepare |
|---|---|---|
| Online assessment | Numerical tests, probability questions or coding, depending on the role | Timed mental math and probability drills |
| Technical interviews | Probability puzzles, expected value, statistics and coding for developer roles | Think out loud and check small cases |
| Final round | Several interviews, sometimes a trading game or market-making exercise | Practice explaining decisions under uncertainty |
Questions that come up, and what strong answers contain
- What is the expected number of rolls of a die to see a six? Set up the expectation clearly and give the answer, six, with the reasoning.
- You flip two coins and one is heads. What is the probability both are heads? Careful conditioning: one third, and why the wording matters.
- Make me a market on the number of cards I will draw before an ace. A sensible range with reasoning, and how you would adjust as you learn.
- Estimate a quantity quickly, such as the number of piano tuners in a city. A clear chain of assumptions and a sanity check.
- Implement a function to compute a moving average over a stream. Constant time per update and correct edge cases.
- What is a fair price for a game where you win the value of a die roll? Expected value, then how risk changes what you would pay.
- Tell me about a time you made a mistake under pressure. What happened, how you fixed it and what you changed.
Two sample answers
You flip two coins and one is heads. What is the probability both are heads?
If all I know is that at least one coin is heads, the possible outcomes are heads-heads, heads-tails and tails-heads, all equally likely, so the probability is one third. If instead I know a specific coin is heads, it's one half. I'd want to confirm which you mean, because the wording changes the answer.
Tell me about a time you made a mistake under pressure.
During a timed group trading game in a finance club, I misread a contract size and took a position twice as large as I meant to. I said so to my team straight away, we reduced it, and we finished slightly positive. Since then I read every contract specification out loud before trading, and I've applied that habit to checking code inputs too.
What interviewers expect from an intern
- Speed with accuracy, and the habit of checking answers.
- Comfort with uncertainty and changing your mind on new information.
- For developer roles, clean and correct code.
For the full-time version of these questions, see Jane Street coding interview questions.
Mistakes that cost offers
- Racing to an answer without checking small cases.
- Freezing instead of reasoning out loud.
- Ignoring the wording of conditional probability questions.
- Treating market-making games as trivia rather than decision-making.
A two-week prep plan
- Days 1 to 4: daily mental math and probability drills under time limits.
- Days 5 to 7: expected value and conditional probability puzzles.
- Days 8 to 10: coding problems if the role needs them, and estimation questions.
- Days 11 to 14: mock interviews and practice explaining each answer step by step.
Timing matters as much as preparation: see our internship recruiting timeline, and once you are in, turning an internship into a return offer. Engineering candidates should also read software engineer intern interview questions.
Where CoPilot Interview fits
Intern interviews reward clear explanations of your own projects and coursework, and that takes practice out loud. CoPilot Interview is an AI interview assistant; its free AI mock interview builds quant intern questions from your résumé and the job description, reads them aloud, scores each spoken answer out of ten and shows a model answer to compare. The free plan gives 15 minutes a day of live help in sessions of up to 15 minutes, with AI mock interviews included, with no card, which suits a student budget. For real interviews and online assessments, follow your employer's rules.
Disclosure: CoPilot Interview is our product, so weigh what we say about it accordingly.
Frequently asked questions
What math do quant intern interviews test?
Mostly probability, expected value, combinatorics, statistics and quick arithmetic. Research roles may add linear algebra or calculus.
Do quant interns need to code?
Developer and research roles usually do; trader roles often focus on math and games, with light coding at some firms.
How can I practice market-making?
Play estimation games with friends, where one person quotes a range and the other buys or sells, and review your reasoning afterward.
Can I use AI tools during an internship interview?
Only where the instructions allow it. Online assessments and many live rounds forbid outside help. Use AI to practice beforehand, and follow your employer's rules.
Practice this interview before the real one
The AI mock interview builds questions from your resume and the job description, reads them aloud and scores each spoken answer out of 10. Included on the free plan.
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