Screenshot: www.geocities.com/faulknerusability
Laura Faulkner has published an Paper “Beyond the Five-User Assumption” in 2003. She tried to disprove Nielsens argument, that five users are enough for good usability testing:
“It is widely assumed that 5 participants suffice for usability testing. In this study, 60 users were tested and random sets of 5 or more were sampled from the whole, to demonstrate the risks of using only 5 participants and the benefits of using more. Some of the randomly selected sets of 5 participants found 99% of the problems; other sets found only 55%. With 10 users, the lowest percentage of problems revealed by any one set was increased to 80%, and with 20 users, to 95%.(…) Although practitioners like simple directive answers such as the 5-user assumption, the only clear answer to valid usability testing is that the test users must be representative of the target population. The important and often complex issue, then, becomes defining the target population.”
related links
Full Paper (PDF)
Laura Faulkner: Website
