Human Factors Issues Chapter 8 Paul King

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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