Designed for Use, 2nd Edition

How Many Testers

Jakob Nielsen famously wrote that only five users are needed to find almost all the usability problems that a larger group would have found.^[155] But even testing with such a small group takes a lot of work. Remember, our goal is to spend only half a day each week. Finding five testers, scheduling them so they can all come in on the same day, making sure somebody takes care of them if they come too early or too late, preparing all the paperwork five times—you can’t do that in half a day.

Instead, you can get useful results by doing only one test with only one person each week.

Before covering the reasons for testing a single user, let’s look at the arguments against it. Nielsen points out two of the disadvantages in his essay. ...