Human Aspects of System Design

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Human Aspects of System Design

• Introduction
• Designing the human element into a system is
  paramount to its success
• One error incorporated by the human into the
  system could bring a major catastrophe
• Some Examples

3 Mile Island Jack Hammers VCR clocks /
programming
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System Design Process

• Molecularization
• System Definition
• Limitation Constraints
• Transformation
• Iteration
• Competition
• Relevance

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Molecularization
Characteristics of a System Design Process
OVERALL TASK
Sub - Task A
Sub - Task C
Sub - Task B
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Characteristics of a System Design Process

• Requirements of the system define options
• Limitations and processes that are unsure

- such as the height required for the legible
picture on a computer screen.
- such as the budget changing, new team
members, innovative ways of manufacturing,
or how parts interrelate.
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Characteristics of a System Design Process

• Transformation
• Time and Cost Constraints

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Characteristics of a System Design Process

• Iterative Cycle

Test and Evaluation
Design
New Information Regarding the System
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Characteristics of a System Design Process

• Competition between groups within the design team
• Relevance to the design

- between sales, administration, manufacturing,
HF - more money / members / power more
influence
- must convince others of the importance of your
contribution in order to get it accepted
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Six Major Stages in the Design Process
Testing and Evaluation
Definition
Implementation
Stage 1
Stage 4
Stage 6
Stage 3
Stage 2
Stage 5
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Six Major Stages in the Design Process

• STAGE 1 System Requirements
• Determine the objectives and principles of the
  process
• Objective
• - purposes of the system
• - general terms
• - details what system is to do to meet
  objectives
• - defines constraints
• System Performance Specifications

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Six Major Stages in the Design Process

• Two HF activities appropriate at Stage 1
• (1) Identify all users of the machine
• (2) Identify the activity-related needs of users
  which the
• system will be responsible for

Examples An oven will be used by a wide range
of users, including families, single people, and
the elderly. Children may use the door as a
stepping stool (possibly to get to the counter)
and thus tipping the entire range over onto them,
possibly killing them.
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Six Major Stages in the Design Process

• STAGE 2 Definition of the system
• Define system functions to meet performance
  criteria

General - not assigned to human, computer, or
software Functions could be short or long,
simple or complex, no real definition as to
the length Functional Flow Diagrams (Figure 22-2
in book)
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Six Major Stages in the Design Process

• STAGE 3 Basic Design
• Allocation of functions to human, computer, and
  software

- sometimes this is considered by economic
considerations or the shear superiority of one
over another - also, there is a gray area, where
both human and machine can both do the job
equally well
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Six Major Stages in the Design Process

• Some Guidelines for Designers

Humans

• reason inductively
• sense unusual events
• sense unexpected events
• develop new solutions

Machines

• monitor for prespecified events
• store and retrieve coded information
• exert considerable physical force
• perform repetitive activities reliably

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Six Major Stages in the Design Process

• Guidelines to Allocate Functions
• (1) Mandatory Allocation

- allocate functions based on system
requirements, hostile environments, safety
considerations, or legal or labor constraints -
these allocations should be made first
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Six Major Stages in the Design Process

• (2) Balance of Value

Human Performance
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Six Major Stages in the Design Process

• (3) Utilitarian and cost-based allocation
• (4) Affective and cognitive support allocations

- functions may be allocated to humans simply
because they are present
Affective support - the emotional requirements of
humans, such as needing challenging work
and feeling personally secure Cognitive support
- the human need for the information to be
relevant so that they can be ready to make
decisions when required
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Six Major Stages in the Design Process

• STAGE 4 Interface Design

• - this stage is performed concurrently with
  STAGE 5 only after the proper allocations of
  functions have taken place
• - this stage deals with designing
• spaces
• displays
• controls
• computer dialogs
• and more
• - this stage is most important for HF
  considerations, though it is usually seen as a
  chore for most engineers

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Six Major Stages in the Design Process
Primary Activities of HF Team in this stage
gather and interpret HF and human performance data
conduct human performance studies
conduct attribute evaluations of suggested
designs
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Six Major Stages in the Design Process

• STAGE 5 Facilitator Design

• Main Focus of this stage Plan for materials
  that will promote acceptable human performance
• Some Examples
• Instruction Manuals
• Performance Aids
• Training Devices
• Training Programs
• Selection
• Some Guidelines for Instruction Manuals
• avoid information overload
• use only concrete information
• remember that learning will come from doing
• users want minimal hassle in setting up

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Six Major Stages in the Design Process

• STAGE 6 Testing and Evaluation

• Evaluation - the measurement of system
  development products (including hardware,
  procedures, and personnel)
• to verify that they will do what they are
  supposed to do
• Human Factors Evaluation -- the examination of
  these products to ensure the adequacy of
  attributes that have implications for human
  performance
• Special Considerations for HF evaluations
• Subjects
• Criteria
• Experimental Procedures and Controls
• Research Setting