Start from the question, not the method. If you need to know why people behave a certain way, use interviews, contextual inquiry, or diary studies. If you need to know whether a design works, use usability testing. If you need to know how many or how often, use analytics or a survey with a real sample. Also weigh time, access to users, and how reversible the decision is.
Why interviewers ask this
Interviewers want to know whether you are method-led or question-led. A designer who runs the same five interviews for every problem is expensive and slow, and one who never talks to users is guessing. They are also checking pragmatism: real teams rarely get eight weeks of discovery, so the strongest answers include how you scale a method down to fit the decision without pretending the result is more certain than it is.
How to structure your answer
- Write the decision you are trying to make before choosing a method.
- Split questions into why, whether, and how many.
- Match the method to the question and to the time you actually have.
- Say what confidence the method buys you and where it is weak.
Example answer
I write the decision down first. Not 'learn about users' but something like 'decide whether to keep bulk actions in the toolbar or move them into a contextual menu'. Once it is phrased as a decision, the method is usually obvious. If I do not understand the behavior at all, I need to watch people work, so interviews or a contextual session where they show me their real setup. If I have a design and want to know whether it is usable, that is a moderated usability test with five or six people per group, and I can get that done in a week. If the question is how often something happens, I go to analytics first, because it is free and instant, and I only run a survey if the event is not instrumented. Constraints are part of the choice, not an excuse. If I have three days, I will do three unmoderated sessions and tell the team exactly what that does and does not prove. Being honest about the confidence level is what keeps people trusting research later.
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See how it worksFollow-up questions to expect
- What do you do when you have no access to real users?
- How do you decide sample size for a qualitative study?
- When is a survey the wrong tool?
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