Clustering for Usability Participant Selection 
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.
Gilbert, Juan E., Andrea Williams, and Cheryl D. Seals. Journal of Usability Studies (2007). Articles>Usability>Testing>Methods