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Week 2: Design
o Introduction to Usability
o The Design
o Design: Defining goals and personas
o CSCW
o Mobile
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Related Questions today???
o What is usability?
o Why is usability important?
o How measuring usability?
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What is poor usability?
To end-users..
I cant findwhat Im
looking for
Its very fancy,but its not very
useful
I find it a bitfrustrating
I dont think itseems trustworthy
Cant it be
more likeGoogle?
I really like it,but I dont use it
much
It doesnt dowhat I need it
to do
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What is poor usability?
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What is Usability???
o User Friendly ???
o Is not a synonym ofusability
o Avoid this expression!
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What is Usability???
o Its not about is this product usable?
o But its about how usable this product?
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What is Usability???
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What is Usability???
o The effectiveness,efficiency,
and satisfaction with which
specified users achieve
specified goals in particularenvironments.
o source: ISO 9241-11
o applies equally to bothhardware and software design
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What is Usability???
ISO 9241-11:
o Effectiveness: The accuracy and completeness with which
specified users achieve their own goals with the system.
o Efficiency: The resources expended in relation to the
accuracyand completeness of goals achieved.
o Satisfaction: The comfort and acceptability of the system
tothe users and other people affected by its use.
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What is Usability???
Jacob Nielson's definition:
oL
ear
nab
ility:
How easy is it for users to accomplish basic tasksthe first time
they encounter the design?
o Efficiency: Once users have learned the design, how quicklycan
they perform tasks?
o Memorability: When users return to the design after a periodof
not using it, how easily can they reestablish proficiency?
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What is Usability???
Jacob Nielson's Definition (cont.):
o Errors: How many errors do users make, how severe are
theseerrors, and how easily can they recover from the errors?
o Satisfaction: How pleasant is it to use the design?
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What is Usability???
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Attributes of usability
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User as starting point
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Why usability is important?
o system development is expensive, and supporting a
poorlydesigned user interface is even more expensive;
o users will reject or work around systems that do not meet
theirneeds;
o design teams need to discover all problems users have in
orderto provide remedies;
o even the best designers are not representative of the users
ofthe system, thus teams need to understand users' perspectivesand
experiences with other systems;
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Why usability is important?
o usability evaluation is an inexpensive way to improve
systems
before they are implemented, to improve existing systems,
and to choose usable systems;
o business users do not have a lot of time to spend learning
how
to use a system;
o businesses cannot train fast enough to keep pace with
attrition
and changing business rules;
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Why usability is important?
o people prefer a usable system with fewer features to a
system
with gratuitous "bells and whistles" which they have to work
hard at figuring out; and
o people often use systems in ways developers did not
expect,
and if designers find this out, they can build these
features
into a new system
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Where?
o Usability testing can be done wherever it is
o in a real work setting
o or in a usability lab
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When???
o During early design stages to:
o Predict product usability
o Check design teams understanding of user requirements
o Test out ideas
o Later in design process:
o Identify user difficulties
(fine tune product)
o Improve upgrade a product
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How conducting usability evaluation?
Usabilitymethods
Testing
Inspection
Inquiry
-Laboratory testing-Thinking aloud
-Heuristic Evaluation-Cognitive Walkthrough
-Focus Group-Questionnaires
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Principles in testing
o Use real users
o Design real tasks
o Record and report the test
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How many subjects?
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How many subjects?
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Setting up usability testing
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Measuring Usability
o What can be measured?
o Performance measures: Counts of actions and behaviours
you can see
o Subjective measures: Peoples perceptions, opinions and
judgments
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Measuring usability
Effectiveness Efficiency User satisfaction
1. Percent task complete
2. Ratio of success tofailures
3. Number of featuresused
1. Time to complete task
2. Time to learn
3. Time spent on errors
1. Rating scale for
usefulness
2. Rating scale for
satisfaction3. Number of times user
express frustration
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Measuring Usability
o Timeo The time taken to complete a task on a computer is
an
obvious metric to choose. Whiteside et al (1985) have
proposed the following empirical relationship:
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Measuring Usability
o Error Rateo All users make errors. The number and type of
errors made
during the performance of a particular task by a user is
clearly an indication of the usability of the system
o Attitude Measureso attitude of the user of a system usually
has to be found by
using questionnaires or interviews. These measures cancover
complete system use, from learnability, to ease of
use, to functionality.
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Measuring Usability
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The Design
Dr. Nor Azman Ismail
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Video example ofBMW iDrive
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Design: Defining goals and personas
Dr. Nor Azman Ismail
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