The Usability Fitness Function

Abstract

The usability fitness function (UFF) is a scale for evaluating user interface designs early in the design lifecycle when it is inexpensive to make changes. The UFF is part of the facilitated genetic algorithm (FGA) design method. The FGA uses a team of designers to generate and evaluate multiple designs in parallel. The evaluation is done by the UFF. The UFF is constructed from evaluation criteria produced by stakeholders in the user interface design (users, human factors and usability engineers, software/hardware engineers, marketing, and project management). The UFF can contain objective, heuristic, and subjective items. The UFF can be scored by either a Likert scale or by magnitude estimation. The Likert scale can order the designs. Magnitude estimation can indicate how many times better or worse a design is than an existing design. The UFF does not replace user testing but prunes bad designs early in the development life cycle thereby saving design cost and resources. This increases the efficiency of user testing, a notoriously resource intensive activity.