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Citadel Securities · Quant researcher · Quant Research (new grad & experienced)

QR: Statistics & Modeling Conversation

An open-ended spoken modeling discussion: regression, model selection, validation, and an end-to-end research case

What they actually ask

The question shapes this round uses. Larpy does not read these out. It builds each one from your own resume, because the generic version is the one you have already rehearsed.

  • “What are the assumptions behind linear regression, and how do you detect when they are violated?”
  • “Explain overfitting and how regularization helps; contrast L1 and L2.”
  • “Describe the bias-variance tradeoff and how it guides model choice.”
  • “How would you check whether a time series is stationary, and why does it matter for modeling?”
  • “Walk me through how you would build and validate a model to predict a noisy signal: data, features, validation, and the main pitfalls.”

What this round is judged on

  • Statistical foundations · regression assumptions, inference, diagnostics
  • Generalization · overfitting, regularization, bias-variance
  • Time-series awareness · stationarity, leakage, validation on temporal data
  • Research judgment · frame an ambiguous problem end to end
  • Communication · defend modeling choices and tradeoffs

Where this round sits

Citadel Securities’s published process. Lime marks the stage this round runs.

  1. 01
    Application / resume screen
  2. 02
    Online assessment (OA)
  3. 03
    Technical phone screen
  4. 04
    Onsite / Superdaythis round
  5. 05
    Hiring decision / committee
What happens in each stage›
Application / resume screen
Recruiter and/or hiring-team screen of resume and background against the target level. SWE and Quant Research (QR) are distinct tracks with overlapping but different loops.
Online assessment (OA)
SWE: HackerRank (occasionally CodeSignal), typically 2-3 hard algorithmic problems, ~60-90 min, strong DS&A bar. QR: heavier probability/statistics/math plus some Python. Format and vendor vary by cycle and campus.
Technical phone screen
One live coding interview (CodePair-style shared editor), ~45-60 min, DS&A focused for SWE. QR phone screens skew to probability, statistics, brainteasers, mental math and light coding.
Onsite / Superday
Multiple back-to-back rounds. SWE commonly: the signature 'evolving problem' coding round, one or more DS&A rounds, a systems / low-level fundamentals conversation (C++ / memory / concurrency), and a behavioral / motivation round. QR: probability & statistics deep-dive, a Python/data coding round, a stats/ML modeling conversation, and a fit round.
Hiring decision / committee
Debrief and hiring decision. Bar is high; strong DS&A and clean, adaptable design are consistently emphasized.

Sources

Built from what Citadel Securities publishes about its own process and from real interview data. No leaked question lists. The questions you get are generated against your own resume, so they are not from anyone else's interview.

Sources last checked . Hiring loops change, so this date is the honest limit on everything above.

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