4.4.3 Efficiency as a Combination of Task Success and Time
Another view of efficiency is that it’s a combination of two of the metrics discussed in this chapter: task success and time on task. The Common Industry Format for Usability Test Reports (ISO/IEC 25062:2006) specifies that the “core measure of efficiency” is the ratio of the task completion rate to the mean time per task. Basically, it expresses task success per unit time.
Share this highlighthttp://www.safaribooksonline.com/a/measuring-the-user/36091/