Assessing the usability of user interfaces: Guidance and online help features.

Abstract

The purpose of this research was to provide evidence to support specific features of a software user interface implementation. A 3 x 2 x 2 full factorial, between subjects design was employed, in a laboratory experiment systematically varying existence or non-existence of a user interface and media of help documentation (either online or written), while blocking for varying levels of user experience. Subjects completed a set of tasks using a computer, so the experimenters could collect and evaluate various performance and attitudinal measures. Several attitudinal measures were developed and validated as part of this research. Consistent with previous findings, this research found that a user's previous level of experience in using a computer had a significant impact on their performance measures. Specifically, increased levels of user experience were associated with reduced time to complete the tasks, fewer number of characters typed, fewer references to help documentation, and fewer requests for human assistance. In addition, increased levels of user experience were generally associated with higher levels of attitudinal measures (general attitude toward computers and satisfaction with their experiment performance). The existence of a user interface had a positive impact on task performance across all levels of user experience. Although experienced users were not more satisfied with the user interface than without it, their performance was better. This contrasts with at least some previous findings that suggest experienced users are more efficient without a menu-driven user interface. The use of online documentation, as opposed to written, had a significant negative impact on task performance. Specifically, users required more time, made more references to the help documentation, and required more human assistance. However, these users generally indicated attitudinal measures (satisfied) that were as high with online as written documentation. There was a strong interaction between the user interface and online documentation for the task performance measures. This research concludes that a set of tasks can be performed in significantly less time when online documentation is facilitated by the presence of a user interface. Written documentation users seemed to perform equivalently with or without the user interface. With online documentation the user interface became crucial to task performance. Research implications are presented for practitioners, designers and researchers.