The Hudson River Trading Probability & Brainteaser Phone Screen interview is stage 2 of 4 in the Hudson River Trading interview process, after the Online Assessment. Format: 45 min - video. A conversational screen on probability and expected value: brainteasers and quick arithmetic, derived out loud with a researcher.
Preparing for this round? Practice the 56 questions mapped to the Hudson River Trading Probability & Brainteaser Phone Screen, with worked solutions. A free account saves your progress.
What the Probability & Brainteaser Phone Screen tests
For Algorithm Developer candidates this is a statistics screen (estimator bias, order statistics, expected value), often followed by checking the answer with a short simulation in code. Software engineering candidates usually skip it and take the programming screen instead.
QuantVault maps 56 practice problems to this round. By topic, the biggest groups are expectation (18), probability (16), statistics (4), game theory (3); by difficulty, 14 easy, 27 medium and 15 hard. 55 of them were reported by candidates who interviewed at Hudson River Trading, most recently in Aug 2026.
Who takes this round: Algorithm Developer (quant research and trading) candidates. See the full Hudson River Trading process and who takes each round.
How to prepare for the Probability & Brainteaser Phone Screen
- Drill the classics until reflexive: Gambler's Ruin, coupon collector, expected waiting times, and conditional-expectation setups.
- Derive out loud and state assumptions; HRT cares how you reason to the answer, not just that you have it.
- Be ready to extend a teaser (the n -> N generalisation) and to sanity-check your result with a limiting case.
- Practice the stats-then-simulate combo: derive an answer, then write a fast numpy Monte Carlo to confirm it - QR interviewers explicitly ask for the simulation.
Further reading: How quant superdays work · Mental math for trading interviews · Behavioral questions at trading firms · Market-making game interview guide.
Question types in this round
The 5 largest question types in the Hudson River Trading Probability & Brainteaser Phone Screen practice set; across them the most common sub-topics are expected value, symmetry, conditional probability, discrete probability, binomial distribution, combinatorics. The questions themselves, with worked solutions, are in the round practice.
Expectation18 in this round
Probability16 in this round
Statistics4 in this round
Game Theory3 in this round
Market Microstructure3 in this round
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Frequently asked questions
What is the Hudson River Trading Probability & Brainteaser Phone Screen interview?
It is stage 2 of 4 in the Hudson River Trading interview process, after the Online Assessment. Format: 45 min - video. A conversational screen on probability and expected value: brainteasers and quick arithmetic, derived out loud with a researcher. For Algorithm Developer candidates this is a statistics screen (estimator bias, order statistics, expected value), often followed by checking the answer with a short simulation in code.
How long is the Hudson River Trading Probability & Brainteaser Phone Screen interview?
Candidates report: 45 min - video.
What questions come up in the Hudson River Trading Probability & Brainteaser Phone Screen interview?
The practice set QuantVault maps to this round centers on expectation, probability, statistics.
How should I prepare for the Hudson River Trading Probability & Brainteaser Phone Screen interview?
Drill the classics until reflexive: Gambler's Ruin, coupon collector, expected waiting times, and conditional-expectation setups. Derive out loud and state assumptions; HRT cares how you reason to the answer, not just that you have it.
What comes after the Probability & Brainteaser Phone Screen?
The Programming Phone Screen (stage 3 of 4). Format: 45-60 min - CoderPad - C++ or Python.
Practice the Hudson River Trading Probability & Brainteaser Phone Screen round
Work the 56 mapped practice problems with progress tracking, then move to the next stage of the Hudson River Trading funnel.