Quant interview preparation: what firms really test
KnowQuant research desk · Published 19 January 2026 · 1 min read
What is asked in a quant interview?
Quant interviews test probability, statistics, mental arithmetic under time pressure, programming, and the ability to reason out loud about an ambiguous problem. Trading seats lean towards fast estimation and market intuition; research seats lean towards statistics and your own past work; development seats lean towards C++, data structures and system design. Almost every process includes at least one question with no clean answer, judged on your reasoning rather than the result.
What this piece establishes
- They are scoring the reasoning, not the answer. The single most common mistake is silence.
- A preparation plan. Work in the order of the seat you want.
- Practise against real structures. Our interview lab lets you filter original practice questions by topic and by the kind of firm, so you can rehearse the specific mix a given process is likely to use.
They are scoring the reasoning, not the answer
The single most common mistake is silence. Interviewers are trying to see how you decompose a problem, what you assume, and whether you notice when your own answer stops making sense. A wrong answer explained cleanly outperforms a right answer produced from nowhere.
The question families
- Probability. Conditional probability, expectation, and games where the trick is setting the problem up correctly.
- Statistics. Estimation, bias, variance, and knowing when a result is noise.
- Mental maths. Fast arithmetic and estimation, especially for trading seats.
- Programming. C++ and Python, data structures, complexity, and - for engineering seats - memory and concurrency.
- Brainteasers and market questions. Fewer than reputation suggests, but not zero.
- Your own work. Expect to be pushed hard on one project you claim to know well.
A preparation plan
Work in the order of the seat you want. Trading: arithmetic and probability daily, then market intuition. Research: statistics depth, then your project narrative. Development: C++ fundamentals, then system design.
Do timed practice out loud. The gap between "I know this" and "I can say this at speed while being interrupted" is where most candidates lose the offer.
Practise against real structures
Our interview lab lets you filter original practice questions by topic and by the kind of firm, so you can rehearse the specific mix a given process is likely to use.
Take this further
Continue in the research index, or look at the employers and pay behind the argument.
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