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Citadel interview questions

90 questions researched across 3 Citadel seats in Quantitative Research, Engineering, Investing. Below are 12 of them.

Seats we researched

  • Quantitative Research Analyst InternQuantitative Research · intern · 45 min
  • Software Engineer InternEngineering · intern · 45 min
  • Investment & Trading InternInvesting · intern · 30 min

12 Citadel interview questions

  1. Let's do some probability. X and Y are positively correlated, and Y and Z are positively correlated. What can you say about the correlation between X and Z?

  2. Coding, talked through: write a function that returns the moving average of a list of numbers over a window of k. How do you make it linear time?

  3. You have a dataset with thousands of features and only a few thousand rows. How would you reduce the dimension, and what are the trade-offs?

  4. How would you describe your research style, and how do you work with collaborators when you disagree about an approach?

  5. What technical area are you most interested in right now, and what have you done about it outside class?

  6. Probability now. If 0.1% of people have a disease and a test for it is correct 99% of the time, whether or not the person has it, what's the chance that someone who tests positive actually has it?

  7. What's the last book you read, and what did you take from it?

  8. Dynamic programming. Daily prices are 7, 1, 5, 3, 6 and 4. With one buy followed by one sell, what's the most you can make, and how does your algorithm find it?

  9. Practical statistics. You regress y on x with 500 observations and get a slope with a t-statistic of 2.5. What does that tell you, and what would make you distrust it?

  10. What does R-squared measure, and can a predictor with an R-squared of 1% still be valuable?

  11. I roll two fair dice. Given that at least one shows a six, what's the probability both are sixes?

  12. Draw two numbers uniformly between zero and one. What's the expected value of the larger one, and the expected distance between them?

What a strong answer does

The questions above fall into 2 kinds. What a strong answer does differs by kind, not by question.

Technical9 of 12 above
State the intuition first; walk through the mechanics; make assumptions explicit; test a risk or edge case; connect the answer to the role.
Behavioral3 of 12 above
Lead with the claim and context; isolate your personal action and decision; explain the trade-off; quantify the result; finish with what you learned and changed.

78 more Citadel questions

The rest of the bank — 90 in total — is asked by the interviewer during practice, so you meet them the way you would on the day rather than reading them first.

Practise Citadel questions

How these questions were researched

Every question carries a provenance grade. Some were reported by candidates who sat the round, some come from the firm’s own published guidance or a source that trains for it, and the rest are written to match how this firm asks. Each seat is studied on its own — the round it actually runs, the order it runs it in, and what it is listening for. A Citadel round is not a generic behavioural screen, and practising one as the other is how people walk in unprepared.

Falas is not affiliated with or endorsed by any employer named. Simulations are independent practice based on publicly described recruiting formats.