15.2 Inspections: heuristic evaluation
15.3 Inspections: walkthroughs
15.4 Predictive models
All the evaluation methods you have encountered so far in this book have involved interaction with, or direct observation of, users. In this chapter we introduce an approach, known as analytical evaluation, where users are not directly involved. This approach includes various inspection methods and predictive models. Inspection methods typically involve an expert role-playing the users for whom the product is designed, analyzing aspects of an interface, and identifying any potential usability problems by using a set of guidelines. The most well known are heuristic evaluation and walkthroughs. Predictive models involve analyzing the various physical and mental operations that are needed to perform particular tasks at the interface and operationalizing them in terms of quantitative measures. They predict the times it will take a user to carry out the same task using different interfaces, enabling different designs to be compared. For example, the optimal layout of the physical and soft keys for a cell phone can be predicted in this way. We cover two of the most commonly used in HCI: GOMS and Fitts' Law.
Inspections are often used to evaluate a fully working system such as a website, whereas predictive modeling techniques are used more for testing specific aspects of an interface, such as the layout of keys or menu options. One ...