Human factors-design of usability

The author discusses the application of human-factors engineering to the development of advanced telecommunication terminals for the office and for public access, to be used by inexperienced users. Ease of use or user-friendly handling is a substantial requirement. The criteria to be observed are the time of use, the error rate, and easy learning. The analysis of the learning process of subjects in many applications yields an exponential function. A usability metric (measure of ease of use) has been defined as an empirical formula. It is shown that this metric depends on a control panel. Using this metric or considering single criteria, the decision whether a terminal is user-friendly should be based on objective measurements (user test) and not only on questionnaires