Measurement of the performance of the user has been an important subject in the field of usability. (User Centered Design, Electronic Performance Support Systems, Human Performance Support). Usability is a vague term if you cannot measure it. However, usability follows a widely accepted standard on how usability should be measured.

The performance of the user is measured by giving this user a task. For this task, the experiment leader measures:

Suppliers can draw up usability requirements for the different tasks people can do with their products. These usability requirements can be tested in a usability test. In a usability test an experiment leader gives a subject of experiment a task. During the performance of the task, the experiment leader makes observations and other recordings. After the subject of experiment has performed the task, the subject of experiment is given a questionnaire that checks his/her satisfaction. The recordings and the questionnaire are used to express the actual usability for that product for that task. The actual usability should be within the required usability.