Authors: Preece, Rogers & Sharp
Introduction
Starters
Chapters
Case Studies
Interactivities
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2 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Chapter Index
Design and Evaluation in the Real World: Communicators and Advisory Systems

Chapter Introduction | Web Resources | Assignment Comments | Teaching Materials


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 of the advantages of analytical methods is that they are relatively quick to perform and do not require involving users to take part in a usability test or field study. However, they are only ever ‘guesses’ of the time it will take for hypothetical users to carry out a given task, or the potential usability problems they might come across when interacting with a product. It requires the usability expert to put themselves in the shoes of another kind of user besides themselves. When reading this chapter imagine yourself as the expert trying to be the hypothetical user and consider how easy or difficult it is.


The main aims of this chapter are to:

  • Describe the important concepts associated with inspection methods.

  • Show how heuristic evaluation can be adapted to evaluate different types of
    interactive products.

  • Explain what is involved in doing heuristic evaluation and various kinds of
    walkthrough.

  • Describe how to perform two types of predictive technique, GOMS and Fitts’
    Law, and when to use them.

  • Discuss the advantages and disadvantages of using analytical evaluation.