The "magic number 5": is it enough for web testing?

Authors:
Nigel Bevan;Carol Barnum;Gilbert Cockton;Jakob Nielsen;Jared Spool;Dennis Wixon
Affiliations:
Serco Usability Services, UK;Southern Polytechnic State University, USA;University of Sunderland, UK;Nielsen Norman Group, USA;User Interface Engineering, USA;Microsoft Corporation, USA
Venue:
CHI '03 Extended Abstracts on Human Factors in Computing Systems
Year:
2003

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Abstract

Common practice holds that 80% of usability findings are discovered after five participants. Recent findings from web testing indicate that a much larger number of participants is required to get results and that independent teams testing the same web-based product do not replicate results. How many users are enough for web testing?