Stop Treating Five Users as a Magic Number
Apply the five-user usability testing heuristic with correct caveats.
Small rounds work best when the users and tasks are meaningfully similar. Small-sample usability testing is powerful because recurring usability problems show up quickly. The practical lesson is to test with a handful of users, fix what you find, and test again. The mechanism is diminishing returns within a reasonably homogeneous user group: the sixth similar participant often repeats issues the first five already exposed. The boundary condition is just as important. If your audience has distinct workflows, permissions, devices, expertise, or accessibility needs, "five users" in one segment does not cover the others. You are sampling interaction patterns, not…
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