User Interface Evaluation CIS 376 Bruce R. Maxim UM-Dearborn

Principles of Good Design State and action alternatives are visible Conceptual model is consistent with system image Interface should include mappings that reveal relationships among task stages User should receive continuous feedback

Where is failure likely as users try to accomplish task goals? Users form inadequate goals Users fail to find the correct interface object due to poor labeling Users might not know how to specify or execute a desired action Users receive poor feedback

Building novel widgets that match user task perceptions Recognize human diversity Use 8 golden rules of user interface design Prevent errors, if at all possible

8 Golden Rules of User Interface Design Strive for consistency Enable short-cuts for frequent users Informative feedback Design dialogs to yield closure Offer simple error handling Permit easy reversal of actions Support internal locus of control Reduce short-term memory load on user

Data Display Guidelines Consistency Efficient information assimilation by user Minimal memory load on user Compatibility between data display and data entry Flexibility of user control over data display

Getting User’s Attention Intensity (2 levels only) Marking (e.g. underscore) Fonts (up to 3) Inverse video Blinking (2 to 4 hertz) Color (up to 4 standard colors) Color blinking Audio

Data Entry Guidelines Consistency Minimal user input actions Minimal memory load on user Compatibility between data entry and data display Flexible user control

Factors affecting choice of evaluation methodology Stage of design Novelty of product Expected number of users Criticality of interface Cost of product and budget for testing Experience of design and evaluation teams

Problems with Testing Can't guarantee perfection When do stop repairing bugs and ship the prototype? Testing focuses on normal product use, not extreme

Review Methodologies Expert Reviews Usability Laboratory Approaches Surveys Acceptance Tests Evaluation During Active Use Classical Experimental Psychology

Expert Review Formats Heuristic evaluation Guideline review Consistency inspection Cognitive walkthrough Formal usability inspection

Usability Laboratory Approaches Think aloud Video tape Field tests Destructive testing Competitive usability testing

Surveys Focus on specific UI features Plan statistical analysis before data collection Consider on-line surveys to increase response rates Use semantically anchored Likert type scales

Acceptance Tests Must be based on measurable criteria Focus on user behavior and task completion

Evaluation During Active Use Interviews Continuous user performance data logging On-line or telephone consulting On-line suggestion box or trouble reports On-line bulletin board or newsgroup User newsletter or conferences