When a User Interface is Good Enough: User Ratings in UI Design

When is the usability of a new user interface design good enough to stop trying to improve it? To answer this question, we propose that usability ratings should be scaled in terms of specific usability criteria, and we evaluated this proposal in an iterative user interface design effort. We also tested our hypothesis that usability ratings arise from the interaction of three user interface dimensions: content, functionality, and layout. We found that scaling usability ratings in terms of specific requirements was effective in identifying when to stop iterating a design, and that ratings of the UI dimensions predicted the usability ratings