Understanding individual results in usability assessments

A central part of the user-centered design process involves evaluating software with its intended users, and is known as usability testing. For usability testing to be effective, recruited participants must be representative of the target population defined through user analysis. Unfortunately, previous research has shown that formal methods for recruiting participants have not been established, and that little is known about the effect of individual differences on usability testing results. This thesis examines the relationship between individual differences, such as personality and experience, on the usefulness and interpretation of usability testing results.;To this end, it first investigates the practices and experiences of usability practitioners when recruiting participants for a usability test. Interviews were conducted with usability practitioners to identify techniques used to characterize and recruit participants, and the problems associated with recruiting unsuitable participants. It then explores the relationship between specific user characteristics, including personality, on usability testing performance. This was done through a usability test showing the relationships between user characteristics and performance. Results indicate gender differences in task performance for difficult tasks, superior communication quality by extroverts and a negative correlation between task completion time and communication performance.