Usability Metrics

It is also possible to collect more specific metrics, such as the percentage of time that users follow an optimal navigation path or the number of times they need to backtrack.

Typically, usability is measured relative to users' performance on a given set of test tasks. The most basic measures are based on the definition of usability as a quality metric:

• success rate (whether users can perform the task at all),


• the time a task requires,


• the error rate, and


• users' subjective satisfaction.