An effort and time based measure of usability
Dan E. Tamir, Oleg V. Komogortsev, Carl J. Mueller · 2008
The hypothesis of this research is that usability relates to the physical effort that is required in order to use software in the accomplishment of interactive tasks. Implications of this hypothesis are significant since effort is an objective quantity that can be measured efficiently in a relatively non-expensive and non-invasive fashion. Based on this hypothesis, this work proposes metrics for measuring operability, learnability, and understandability.