📖 Notes
LESSON 17 OF 26
Usability Testing — The 5-User Rule
Watching Real People Use Your Design
How to run a usability test — task-based testing, think-aloud protocol, and why 5 users is usually enough.
Running a Test
Tasks, Think-Aloud, and Sample Size
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Task-Based Testing
Give participants a realistic goal ("find and book a flight") rather than asking their opinion of the design.
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Think-Aloud Protocol
Ask participants to narrate their thoughts as they work, surfacing confusion in the moment it happens.
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The 5-User Rule
Nielsen Norman Group research found testing with 5 users typically surfaces around 85% of usability problems.
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Iterative Rounds
Better to test 5 users, fix issues, then test 5 more than to test 15 users once.
Why 5 Users, Not 50
Usability problems are heavily repeated across users — the same issues surface again and again. Beyond about 5 participants, each additional person mostly re-confirms problems you've already found, so testing smaller and more often beats one large study.
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Don't lead the witness
Avoid questions like "Was that easy to find?" — ask "What would you do next?" and let the participant's actual behavior reveal the answer.