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HF & User Interface Development Process
Quantifying
Human
Performance
Measuring and qualifying human performance and levels of comfort in the
user-product relationship can be affected by many factors such as age,
physical health, energy level – stamina, mental and physical endurance,
circadian rhythms, state of mind, attitude, emotions, propensity
for certain common mistakes, errors and cognitive biases, etc. Defining
human reliability and error limitations are very important
to define and
meet safety requirements and
the adverse consequences and dangers of human errors or
oversights, especially when the human-product interface is a crucial
part of the design while helping to make products and technology applications
safer and better suited
for operation by the intended users - humans.
Human Error
The cognitive study of the user product interface and human error
relates to limits of memory and attention and the decision making
processes. There are a variety of methods for testing and
analyzing human reliability. Ways to categorize human
error include: (Jones, 1999)
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exogenous versus endogenous (i.e., originating outside versus inside
the individual) (Senders and Moray, 1991)
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situation assessment versus response planning (i.e., Roth et al, 1994)
and related distinctions in
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errors in problem detection
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errors in problem diagnosis
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errors in action planning and execution (Sage, 1992) (for example:
slips or errors of execution versus mistakes or errors of intention;
Norman, 1988; Reason, 1991)
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By
level of analysis; for example, perceptual versus cognitive versus
communication versus organizational. (Optical illusions)
User Interface - Time and Motion Studies
A time and motion study
is a efficiency technique combining the time study work of Frederick
Winslow Taylor with the motion study work of Frank and Lillian Gilbreth.
A time and motion study is used to analyze and reduce a product
interaction process or man - machine system tasks by defining the number and
range of motions and time to perform a single task, in order to increase
productivity. Reducing range of motion in hand-eye coordination, limb or hand task or
walking or lifting articulation, while considering evaluation under
various human emotional states such as normal - alert, tired - sleepy,
physically - stressed, mentally- stressed, etc,) including the study of
static and dynamic weight or forces on biological and mechanical
joints or tensors (CAD simulation) which can be classified based on
bio-mechanical properties. According to the anatomic classification,
joints are subdivided into simple and compound, depending
on the number of bones involved, and into complex and
combination joints.
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Simple Joint: 2 articulation surfaces (eg. shoulder joint, hip joint)
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Compound Joint: 3 or more articulation surfaces (eg. radiocarpal
joint)
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Complex Joint: 3 or more articulation surfaces (i.e. articular disc)
Considerations
When evaluating a
user-product interface for usability and user-friendly attributes, our
designers must set up testing procedures which establishes a base line
and qualifies the articulation
and normal range of motion of users and while performing interaction or
interface tasks with respect to time, to define efficiency and reliability. Human factors testing is
looking to reduce movement and the learning curve, reducing error, while
improving performance, speed and reliability. To
answer these
questions, the Industrial Designer must explore the extremes and ask the
tough questions to probe and consider both the physical and
psychological state of the individual users. This human performance,
reliability and human error data can be obtained by conducting user and
task analysis and time motion studies at the start of the project.
During the study, you may consider asking these questions:
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Can
users easily accomplish their intended tasks? For example, can users
accomplish intended tasks at their intended speed?
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How
much training do users need?
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What
documentation or other supporting materials are available to help the
user? Can users find the solutions they seek in these materials?
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What
and how many errors do users make when interacting with the product?
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Can
the user recover from errors? What do users have to do to recover from
errors? Does the product help users recover from errors? For example,
does software present comprehensible, informative, non-threatening
error messages?
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Are
there provisions for meeting the special needs of users with
disabilities? (accessibility)
Examples of ways to find
answers to these and other questions are: user-focused requirements
analysis, building user profiles, and usability testing to define the
most appropriate product design solution.
Human Factors & Ergonomics:
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