Communicating: structuring an answer and defending an assumption
CASE · Chapter 611 min readAsked at Two Sigma, QuantCo, Citadel, Point72
Assumes Data quality: missingness, outliers, regimes and leakage.
After this lesson you should be able to
- Structure a verbal answer so the interviewer can follow and redirect it.
- Defend an assumption without either folding or digging in.
- Say what an open case is actually scored on.
An open case is assessed on how you think, and thinking is only visible when it is narrated. The candidates who do badly are frequently the ones who reason well in silence and present a conclusion — because the conclusion was never the thing being marked.
Proposition 6.1
Signpost, then reason
Say what you are about to do, do it, then say what you concluded and what comes next. "First I want to pin down the target, then I will list the data I would want" costs five seconds and lets the interviewer redirect you before you spend ten minutes on the wrong branch — which is the single most common way a strong candidate wastes an interview.
Holds when
- Number your points aloud. "Three things worry me here" commits you to a structure and makes it easy to follow.
- Say when you are moving on, so the interviewer knows a section is finished.
- If you need to think, say so and think — silence with a warning is fine, silence without one is not.
Proposition 6.2
State assumptions as assumptions
Every open case requires assumptions, and stating them explicitly converts a guess into a premise the interviewer can accept or correct. "I will assume we have point-in-time fundamentals; if not, the whole approach changes" is strong. Using the same assumption silently and being caught on it later is not.
Holds when
- Rank them: say which assumption, if wrong, would do the most damage.
- Offer the alternative branch briefly, so it is clear you know the answer is conditional.
- Assumptions you state and the interviewer accepts are no longer your risk.
How to handle pushback. Pushback is almost always a test rather than a correction, and both possible failures are visible. Folding immediately suggests you had no reason for the choice; refusing to move suggests you cannot update on evidence. The correct response is to ask what specifically they disagree with, then either give the reason you chose it or change it explicitly and say what that does to the conclusion. Changing your mind for a stated reason is the behaviour being looked for — it is what a researcher does when a result contradicts a prior.
| Dimension | What good looks like |
|---|---|
| Structure | A stated order of attack, followed |
| Problem definition | Target, horizon and decision pinned down early |
| Data scepticism | Asking what is knowable when, unprompted |
| Baseline | Something simple proposed before anything clever |
| Self-criticism | Naming what would falsify the approach |
| Communication | The interviewer can follow without asking |
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