Clustering for Usability Participant Selection
http://www.usabilityprofessionals.org/upa_publications/jus/2007november/gilbert.html
  peer-reviewed

Gilbert, Juan E., Andrea Williams, and Cheryl D. Seals
Journal of Usability Studies
2007

Abstract:

User satisfaction and usefulness are measured using usability studies that involve real customers. Given the nature of software development and delivery, having to conduct usability studies can become a costly expense in the overall budget. A major part of this expense is the participant costs. Under this condition, it is desirable to reduce the number of participants without sacrificing the quality of the experiment. If a company could use a smaller participant pool and get the same results as the entire pool; this would result in significant savings. Given a participant pool of size N, is there a subset of N that would yield the same results as the entire population? This research addresses this question using a data-mining clustering tool called Applications Quest.