18.1 Introduction

Usability testing can take many forms, for instance, expert inspections, employment of "user representatives" for their opinions, and various forms of automated testing. Nevertheless, in a survey published by the Usability Professionals' Association in 2001, "usability evaluation with real users" was the most popular activity cited by the respondents (Usability Professionals Association, 2001). Usability evaluation (sometimes called testing) refers to two different activities. It is customary, following terms used in educational psychology (Scriven, 1967), to call these formative and summative modes of test.

Formative modes of test take place during the activity of developing the software or Web site, and the goal of these activities is to improve the product by providing specific feedback to the design team of which aspects of the software or Web site are usable and which aspects need improvement.

Summative modes of test take place when the product has reached a certain stage of development, and the primary goal of these latter activities is to show how much progress has been made in the development of a usable product. Summative testing is a term widely used in usability, although it has not yet found general acceptance. Other terms used have included usability validation, user validation and user acceptance test. In some quarters, the term test is depreciated in favor of the less-intimidating words study or evaluation.

This chapter focuses on summative testing. In contrast to...