Transcript International Workshop 28 Jan – 2 Feb 2011 Phoenix, AZ, USA What is Usability Usability Presentation by Jen Narkevicius.

International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
What is Usability
Usability Presentation by Jen
Narkevicius
Philosophy
International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
• We want to measure usability in order to
incentivize and reward developers for
designing products that are easy to learn,
efficient to use, tolerant of missteps, and
provide a satisfactory experience for the user
• Benefits to the community and the developers
– Wider user populations
– Broader and more consistent use
– Better understanding of the models and their
meaning
– Increased sales
Lund Usability Maxims
(in descending order of importance)
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International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
Know the user. YOU are not the user
Things that look the same should act the same/ Things that look different should act different
The information for the decision must be there when the decision is needed
Error messages should actually mean something to the user and tell the user how to fix the problem
Every action should have a reaction
Everyone makes mistakes, so every mistake should be fixable
Don't overwhelm the user
Consistency, consistency, consistency
Minimize the need for a mighty memory
Keep it simple
The user should always know what is happening
The more you do something, the easier it should be to do
The user should control the system. The system should not control the user. The user is the boss and
the system should show it
Eliminate unnecessary decisions and illuminate the rest
The best journey has the fewest steps. Shorten the distance between the user and the goal
Users should be able to do what they want
Lund, A. M. (1997). Expert ratings
Alert users to an error before things get worse
of usability maxims. Ergonomics in
Users should always know how to find out what to do next Design, 5(3), 15-20. A study of the
heuristics design experts consider
Strive to empower the user, not speed up the system
important for good design.
International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
Definitions
• Usability = The extent to which a product can be
used by specified users to achieve specified
goals with effectiveness, efficiency, and
satisfaction in a specified context of use or a
quality attribute that assesses how easy user
interfaces are perceived to be to use. Also refers
to methods for improving ease-of-use during the
design process.
• Task = activity performed by a single person that
has a distinct beginning and end
• Function = a related set of tasks, some of which
may be automated (i.e., performed by a
computer). May consist of multiple people
performing cooperative or collaborative tasks
Measurable Usability Dimensions
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Ease of Learning
Efficiency of Use (routine)
Efficiency of Use (non-routine)
Error Tolerance
Subjective
International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
Ease of Learning
International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
• After providing some opportunity for a new
user to learn how to perform a function (e.g.,
demonstration, exploration, documentation),
assess how well the user can perform a
related task
– Near-transfer - very similar task
– Far-transfer – different task that requires the user
to draw inferences from what they learned
• Motivation: Reward products that support
transparent mental models and that provide
consistency in the interface
Efficiency of Use
International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
• Measured by number of steps (button clicks) or by the
elapsed time to perform a well-defined function (set of
tasks)
• Measure for routine tasks and non-routine tasks
• Motivation – Reward products that limit unnecessary
steps and provide convenient shortcuts for routine
tasks
Subjective
International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
• Qualitative measure of how much the user
liked using the product. Typically measured
by questionnaire on a ranked scale.
– Was it compelling?
– Was it satisfying?
– Would you want to use this product again?
• Motivation: Rewards elegance, clarity, and
user satisfaction
Cautions
International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
• Complex products offer challenges for unbiased
testing
– Certainly need a combination of skilled users (perhaps
even the product developer) and users that understand the
intent of the tool but have no experience with the specific
product
• Beware of unintended consequences
– “rats go after pellets”
• Must select and carefully design the functions being
tested to examine a reasonable breadth and depth
of functionality
– Resist the temptation to assess “Cadillac” functions before
ensuring “Chevy” functions are covered
Conclusion
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International Workshop
28 Jan – 2 Feb 2011
Phoenix, AZ, USA
History
Accomplishments
Concepts of Operation
Plan
Use Cases
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