1. Human Factors Issues
Chapter 8
Paul King

2. What is Human Factors?
Application of the scientific knowledge of human capabilities and limitations to the design of systems and equipment to produce products with the most efficient, safe, effective, and reliable operation

3. Human Factors Interface points Environment Skill level of user
Interaction between:
Human element
Hardware element
Software element

4. Human Element Memory Thinking and reasoning Visual perception
Long term
Short term
Thinking and reasoning
Visual perception
Dialogue construction
Individual skill level
Individual sophistication

5. Hardware Element Size limitations Location of controls
Compatibility with other equipment
Potential need for portability
Possible user training
Display area
Control knobs/switches

7. Software element Simple, reliable data entry Menu driven
Displays must not be overcrowded
Dialogue must be jargon-free
Feedback to users

8. Human Factors Process
Analytic process that focuses on device objectives
Design and development process that converts results of analyses into detailed equipment features
Test and evaluation process which verifies that development process satisfies constraints

9. Steps in Human Factors Process
Planning
Analysis
Conduct user studies
Observations
Interviews
Focus groups
Task analysis
Benchmark usability tests
User profile
Setup advisory panel

10. Steps in Human Factors Process (cont.)
Set usability goals
Provide quantitative basis for acceptance testing
Objective or subjective
Design user interface concepts
Develop conceptual model
Develop user interface structure
Define interaction style
Develop screen template
Develop hardware layout
Develop final design

11. Steps in Human Factors Process (cont.)
Model the user interface
Build a prototype to evaluate dynamics of user interface
Test user interface
At start of development effort
When prototype is developed
When marketing claims may be displayed

12. Specifying the User Interface
Style guide
Screen hierarchy map
Screenplay
Specification prototype
Hardware layouts

13. Additional Human Factors Design Considerations
Consistency and simplicity
Safety
Environmental/Organizational Considerations

14. Documentation Written to meet needs of various target populations
Study capability and information needs of documentation users
Mental abilities
Physical abilities
Previous experience
Understanding of general operation
Special needs of environment

15. Anthropometry
Science of measuring human body and its parts and functional capacities
Range of values: 5th percentile female to 95th percentile male
Functional dimensions
Psychological elements
Workstation design considerations

16. Alarms and Signals Purpose is to draw attention of operator
3 categories:
High priority: immediate response required
Red flashing light
Medium priority: prompt response required
Yellow flashing light
Low priority: awareness required
Steady yellow light
Audible signal when not in line of sight

17. Labeling Labels should be clear and direct
Controls, displays, and other equipment that must be located should be clearly marked
Receptacles and connectors should be marked with intended function or connection
Hazard warnings should be prominent

18. Software
Every user input should consistently produce some perceptible response from the computer
Log-on should be automatically completed before any operation
Allow for orderly shutdown in case of failure

19. Data Entry Consistent data entry transactions
Minimize user input actions
Feedback to user about acceptance or rejection of an entry
Ability to change entry after it has been added

20. Displays Visual displays should clearly indicate system status
Graphic displays should be used when perception of pattern of variation is important
Numeric displays should be sued when quantitative accuracy is important
Displays should be consistent

21. Interactive Control
System response times should be consistent with operational requirements
Control-display relationships should be straightforward and explicit
Menu selection for interactive controls

22. Feedback
Present status, information, confirmation, and verification throughout the interaction
Standby should be accompanied by ‘WAIT’ message
Feedback should be self-explanatory

23. Prompts
Commands, error messages, system capabilities, and procedures should be explained with prompts or help instructions
Missing data/aborting changes should be prompted
Factual and informative dialogue
Displayed in standardized area

24. Defaults
Currently defined default values should be provides and automatically displayed
User should be prompted for acceptance of defaults
Users should be able to set their own default