1. Human-Computer Interaction

2. Software Usability: Usability Criteria
Learnability
Time to learn.
Issue: learn how well?
Efficiency
Degree to which system supports user performance.
Time efficiency.
Procedural efficiency (number of steps).
Memorability
Extent to which use procedures can be remembered.
Issue: Casual users and intermittent use.

3. Software Usability: Usability Criteria (2)
Errors
Extent to which software induces errors.
User “traps”.
Issue: Violation of arbitrary standard may not be an error.
User Satisfaction
Subjective estimation.
Rating scales.

4. Task and User Characteristics
Task frequency
Discretionary vs. mandatory use
Types of users
novice
knowledgeable intermittent user
expert frequent user

5. Theories, Models, and Metaphors
Norman’s seven stages of action model
1. Establish the goal.
Carry out an action by:
2. Forming an intention
3. Specifying the action sequence (planning)
4. Executing the action sequence (execution)
Assess the effects of the action by
5. Perceiving the system state
6. Interpreting the state
7. Evaluating the system state with respect to the goal and intentions

6. GOMS Modeling Goals Operators desired end, result
e.g., new version of a Word document (original preserved)
Operators
steps that can be performed towards achieving the goal
e.g., open document in Word, copy file

7. GOMS Modeling (2) Methods Selection Rules ordered set of operators
e.g., “Save From Word”:
open document in Word
Save As new name
Selection Rules
Rules to select which method to use
e.g.,
IF currently using Word
THEN use “Save From Word” method
IF currently using Windows Explorer
THEN use “Copy and Rename”

8. Models and Metaphors Conceptual model/metaphor Mental model
Real-world task that helps user interact with the system
e.g.,
cut-and-paste
desktop metaphor
spreadsheet metaphor
Mental model
How the user thinks about how the software works: beliefs about
parts of the software
how the parts interact
what functions can be performed
how to perform those functions

9. Conceptual Models vs Mental Models
Goal: Design interface so that user quickly develops an “accurate” mental model.
Approach:
make invisible parts visible
provide feedback
be consistent
present functionality through a familiar metaphor

10. Basic Screen Design Principles
General Layout
Text
Numbers
Coding Techniques
Color

11. General Layout Principles
Include only essential information.
Include all essential information.
Start in upper left corner.
Develop and follow formatting standards.
Group items logically.
Provide symmetry and balance.
Avoid use of ALL UPPER CASE.
Distinguish captions (field labels) and fields.

12. Text Principles Make messages concise.
Text should be simple, specific, comprehensible, and clear.
Use level of detail appropriate to user and task.
Make messages constructive, not critical.
Message should imply that user is in control.
Use wording consistent with appropriate action.

13. Text Principles (2) Place instructional prompts when and where needed.
Use active voice.
Avoid negatives.
Order prompts chronologically.
Format prompts for easy scanning.
Use consistent terminology.

14. Number Principles Right justify numbers. Decimal-align real numbers.
Avoid leading zeros.
Group digits with appropriate separators.

15. Coding Techniques Principles.
Use attention-getting techniques appropriately and cautiously.
Limit size coding to 5 sizes.
Use 2-4 different character types.
Use geometric shapes.
Use borders to group items.

16. Color Principles Use color sparingly.
Use color to draw attention, organize, and indicate status.
Use color to support search tasks.
Back up color coding with redundant cues.
Use color consistently
Limit color coding to 8 colors.
Avoid saturated blues for text.
Choose color combinations carefully.

17. Nielson’s General Usability Principles
Match between system and real world
Consistency and standards
Visibility of system status
User control and freedom
Error prevention, recognition, and recovery
Memory
Flexibility and efficiency of use
Simplicity and aesthetic integrity

18. Match between system and real world
Speak the user’s language.
Use familiar conceptual models/metaphors
Follow real-world conventions
Input cues map onto user’s goals

19. Consistency and standards
Be consistent throughout the interface
Use color coding uniformly
Use uniform input syntax
Show similar information on the same place on each screen
Logically group functions
Conform to platform (e.g., Windows) interface conventions

20. Visibility of system status
Keep user informed about what’s going on
Show that input has been received
Change features as task is accomplished
Provide feedback for all actions
Indicate progress in task performance
Make feedback timely and accurate
Use direct manipulation

21. User control and freedom
Be forgiving (undo, redo)
Mark exits clearly
Provide ability to reorder or cancel tasks
Allow user to initiate/control actions
Avoid modes

22. Error prevention, recognition, and recovery
Prevent errors from occurring
Help users recognize, diagnose, and recover from errors
Use clear, explicit error messages

23. Memory Use see-and-point rather than remember-and-type
Make set of available options visible
Make everything needed available through the GUI
Provide lists of choices
Use direct manipulation
Evoke goals in the user

24. Flexibility and efficiency of use
Provide shortcuts, accelerators
Provide customization to speed up actions
Make system efficient

25. Simplicity and aesthetic integrity
Make interface look good with simple graphic design
Use simple, natural dialog
Avoid clutter
Put information in natural and logical order

26. Application of the Principles
Microsoft Word
Dreamweaver MX
Mozilla Composer
FAA Certification Job Aid document anotation form (MS Access)

31. Steps in Software Interface Design
Phase 1: Scoping
1. Develop project plan: scope and schedule.
2. Develop user profile.
3. Define hardware, software platform, interface techniques.
Phase 2: Functional Specification
4. Perform task analysis.
5. Set user interface goals, specify minimum performance levels.
6. Define training and documentation.

32. Steps in Software Interface Design (2)
Phase 3: Design
7. Develop mockup: storyboard, rapid prototyping, etc.
8. Develop style guide.
9. Perform detailed user interface design.
10. Develop interface prototype.
11. Write prototype user interface test plan.
12. Perform prototype user interface testing. Redesign.

33. Steps in Software Interface Design (3)
Phase 4: Development
13. Develop training and documentation.
14. Develop user interface test plan.
Phase 5: Testing/Implementation
15. Conduct user interface testing. Iterate.
16. Evaluate final user interface.

34. Software Usability Metrics
Effectiveness
Percent tasks completed
Ratio of successes to failures
Number of features/commands used
Workload
Efficiency
Time to complete task
Time to learn
Time spent on errors
Percent/number of errors
Frequency of help/documentation use
Number of repetition of failed commands

35. Software Usability Metrics (2)
User Satisfaction
Usefulness rating
Satisfaction rating
Number of time dissatisfaction expressed
Rating of user vs computer control
Perception that software supports task