Usability Views Article Details  home | timeline | recent | popular | e-reports | userati | books | about  Evaluating the 'test-five-users' guideline (01 May 2004) Over the 100 simulated tests, the percentage of usability problems found when testing five participants ranged from nearly 100% down to only 55%. As any good freshman statistics student could predict, there is a large variation in outcomes between trials with small samples. Extrapolating from Faulkner's findings, usability test designers relying on any single set of five users run the risk that nearly half the problems could be missed. Article URL: http://www.humanfactors.com/downloads/may04.asp Read 31 more articles from Human Factors International sorted by date, popularity, or title. Next Article: Keeping up with the Joneses This site is a labour of love built by Chris McEvoy