User Interface Evaluation

1
User Interface Evaluation

• CIS 376
• Bruce R. Maxim
• UM-Dearborn

2
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

3
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

4
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

5
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

6
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

7
Getting Users 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

8
Data Entry Guidelines

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

9
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

10
Problems with Testing

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

11
Review Methodologies

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

12
Expert Review Formats

• Heuristic evaluation
• Guideline review
• Consistency inspection
• Cognitive walkthrough
• Formal usability inspection

13
Usability Laboratory Approaches

• Think aloud
• Video tape
• Field tests
• Destructive testing
• Competitive usability testing

14
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

15
Acceptance Tests

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

16
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