Usability evaluation helps to determine whether interactive systems support users in their work tasks. However, knowledge about those tasks and, more generally, about the work-domain is difficult to bring to bear on the processes and outcome of usability evaluation. One way to include such work-domain knowledge might be Cooperative Usability Testing, an evaluation method that consists of (a) interaction phases, similar to classic usability testing, and (b) interpretation phases, where the test participant and the moderator discuss incidents and experiences from the interaction phases. We have studied whether such interpretation phases improve the relevance of usability evaluations in the development of work-domain specific systems. The study included two development cases. We conclude that the interpretation phases generate additional insight and redesign suggestions related to observed usability problems. Also, the interpretation phases generate a substantial proportion of new usability issues, thereby providing a richer evaluation output. Feedback from the developers of the evaluated systems indicates that the usability issues that are generated in the interpretation phases have substantial impact on the software development process. The benefits of the interpretation phases may be explained by the access these provide both to the test participants’ work-domain knowledge and to their experiences as users.

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