Product Designer interview question
How do you run usability testing?
Set research questions and representative tasks, recruit target users, use a realistic prototype without leading them, observe behavior and success, probe after tasks, separate severity from frequency, and prioritize evidence-backed changes.
Direct answer
What a strong answer covers
How it works
A usability test answers whether people can accomplish specific tasks with a design, and why not when they cannot. The plan states the research questions and turns them into realistic tasks with success criteria, recruits five to eight participants who match the target users, and uses a prototype or build realistic enough that behaviour transfers. The facilitator gives the task, then stays quiet, watching what participants do and where they hesitate, asking questions only after each task to avoid leading. Findings are rated by severity, how badly the issue blocks the task, separately from frequency, and the report prioritises fixes by the combination, with clips as evidence.
Example
Testing a new expense submission flow, six employees were asked to submit a receipt for a client dinner with two attendees. Four of six failed to find the attendee field, which was collapsed under an advanced section, rated high severity and high frequency; two paused at the currency selector, low severity. The attendee field was moved into the main form before development, and the currency default was set from the user’s locale.
Common mistakes
- Explaining the interface before the task and then measuring whether people can use it.
- Asking leading questions such as was that easy during the task.
- Reporting a list of complaints without severity, so the team fixes the loudest rather than the worst.
A useful answer structure
Answer from your own work.
Do not memorise a script: use only examples you can explain honestly in follow-up questions.
Open the desktop workspace and rehearse a clear answer in your own words.