Reviewing and extending the five-user assumption: a grounded procedure for interaction evaluation

Borsci, Simone; Macredie, Robert D.; Barnett, Julie; Martin, Jennifer L.; Kuljis, Jasna; Young, Terry

Abstract

The debate concerning how many participants represents a sufficient number for interaction testing is well-established and long-running, with prominent contributions arguing that five users provide a good benchmark when seeking to discover interaction problems. We argue that adoption of five users in this context is often done with little understanding of the basis for, or implications of, the decision. We present an analysis of relevant research to clarify the meaning of the five-user assumption and to examine the way in which the original research that suggested it has been applied. This includes its blind adoption and application in some studies, and complaints about its inadequacies in others. We argue that the five-user assumption is often misunderstood, not only in the field of Human-Computer Interaction, but also in fields such as medical device design, or in business and information applications. The analysis that we present allows us to define a systematic approach for monitoring the sample discovery likelihood, in formative and summative evaluations, and for gathering information in order to make critical decisions during the interaction testing, while respecting the aim of the evaluation and allotted budget. This approach -- which we call the Grounded Procedure -- is introduced and its value argued.

Citation

Borsci, S., Macredie, R. D., Barnett, J., Martin, J. L., Kuljis, J., & Young, T. (2013). Reviewing and extending the five-user assumption: a grounded procedure for interaction evaluation. ACM Transactions on Computer-Human Interaction, 20(5), Article 29. https://doi.org/10.1145/2506210

• Journal Article Type: Article
• Publication Date: Nov 1, 2013
• Deposit Date: Jul 30, 2015
• Publicly Available Date: Jul 30, 2015
• Journal: ACM Transactions on Computer-Human Interaction (TOCHI)
• Electronic ISSN: 1073-0516
• Publisher: Association for Computing Machinery (ACM)
• Peer Reviewed: Peer Reviewed
• Volume: 20
• Issue: 5
• Article Number: 29
• DOI: https://doi.org/10.1145/2506210
• Public URL: https://nottingham-repository.worktribe.com/output/718169
• Publisher URL: http://dl.acm.org/citation.cfm?id=2506210&CFID=697895576&CFTOKEN=48685461
• Additional Information: © ACM, 2013. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Transactions on Computer-Human Interaction, Vol. 20, Issue 5, 2013. http://doi.acm.org/10.1145/2506210