Relationship between certain objective performance measures and subjective usability

The nature of the relationship between objective and subjective usability measures is thought to be a positive one, though little else is known. It is this relationship that is to be investigated in this study. The objective is to determine a “figure of merit” (FOM) incorporating the most important objective usability characteristics that can successfully predict the satisfaction characteristic.; The usability literature was surveyed to determine the most commonly cited objective and subjective usability characteristics and measures. Six objective usability characteristics were determined to be important: Learnability, Relearnability, Guessability, Flexibility, Effectiveness, and Efficiency. These objective characteristics coupled with Satisfaction, were presented to experts for pair-wise comparison to determine the perceived importance of each characteristic to usability as a whole.; A rank order of the characteristics was obtained and a Kendall's Coefficient of Concordance (Kendall's W) was calculated to determine the level of agreement between the rankings. Little agreement was found among the rankings. One by one, the characteristics were dropped from consideration and the Kendall's W was recalculated to find the combination of characteristics with the highest amount of agreement among the experts. At the end of this process only four objective characteristics remained: Effectiveness, Efficiency, Guessability and Learnability.; A web-based usability evaluation study was then performed during which measures of the four characteristics were automatically taken and collected, and compared against the satisfaction measure obtained from the participants of the study. Results show that the objective characteristics are independent of each other and could predict the satisfaction characteristic.; Based on the findings of this study, two proposals are made for a relative Figure of Merit (FOM). Both FOMs are constructed using the four objective characteristics as determined by the paired comparison; one involves summation, the other multiplication. The relative merits of both proposed FOMs are left for further investigation. Both FOMs allow differentiation between the websites and seemingly achieve the objective of predicting user satisfaction.