A usability test measured the number of errors made in performing a task with a...

The sample includes only six users out of an intended population of 500 users, so it is too small to support a strong conclusion about overall usability. Software quality engineering emphasizes representative sampling when evaluating usability, reliability, performance, and user behavior. The data shows variation, including one user with 12 errors, but that value should not automatically be removed unless there is a valid assignable cause. The average is not 6 errors; it is 28 divided by 6, or about 4.67 errors. Also, no acceptance criteria are provided, so the error levels cannot be judged acceptable. The most valid conclusion is that more usability testing should be performed with additional groups of representative users.

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