Training · QF-1 · Lesson 05 of 05

The quant interview

The rule

Expect probability, expected value, and a coding problem under time pressure — plus a demand that you explain something you have built.

Interview stages

Expect an online test (maths, logic, coding), phone screens on probability and statistics, and a final round with research discussions, coding and brainteasers. Research roles may include a presentation of your past work.

Probability and expected value

Classic questions involve dice, coins, cards and betting games. State the setup, define the random variable, compute the expectation, and check with intuition.

Example: roll a die, paid the face value; may re-roll once

EV of one roll: 3.5
Strategy: Keep 4, 5, 6; re-roll 1–3
EV: 0.5 × 5 + 0.5 × 3.5
Answer: 4.25

Statistics and linear algebra

Be fluent in conditional probability and Bayes, distributions, variance of sums, regression assumptions and interpretation, correlation versus causation, and eigenvalues and covariance matrices. Expect questions on overfitting and how you'd detect it.

·Explain p-values plainly.
·Derive OLS coefficients.
·Explain why adding variables raises R² even when useless.

Coding

Coding tests range from algorithm questions to data manipulation with pandas or implementing a simple backtest. Clean, correct code beats clever code. Talk through complexity and edge cases.

Discussing your research

Be ready to explain a project end to end: question, data, method, results, and how you guarded against bias. Interviewers value candidates who can say what did not work and why.

Hold onto this

·Practice brainteasers as spoken reasoning: say the setup, then the answer.
·Be fluent in expectation, variance, Bayes, and simple simulation.
·Bring one project where you can defend the data, the method and the failure case.

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Education, not financial advice. Figures may be simplified for illustration.