-
Usability
-
Whats on today???
o What is usability?
o Why is usability important?
o How measuring usability?
-
What is poor usability?
To end-users..
I cant find what Im
looking for
Its very fancy, but its not very
useful
I find it a bit frustrating
I dont think it seems trustworthy
Cant it be more like Google?
I really like it, but I dont use it
much
It doesnt do what I need it
to do
-
What is poor usability?
-
What is Usability???
o User Friendly ???
o Is not a synonym of
usability
o Avoid this expression!
-
What is Usability???
o Its not about is this product usable?
o But its about how usable this product?
-
What is Usability???
-
What is Usability???
o The effectiveness, efficiency, and satisfaction with which
specified users achieve
specified goals in particular
environments.
o source: ISO 9241-11
o applies equally to both
hardware and software design
-
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
accuracy
and completeness of goals achieved.
o Satisfaction: The comfort and acceptability of the system
to
the users and other people affected by its use.
-
What is Usability???
Jacob Nielson's definition:
o Learnability: How easy is it for users to accomplish basic
tasks
the first time they encounter the design?
o Efficiency: Once users have learned the design, how
quickly
can they perform tasks?
o Memorability: When users return to the design after a
period
of not using it, how easily can they reestablish
proficiency?
-
What is Usability???
Jacob Nielson's Definition (cont.):
o Errors: How many errors do users make, how severe are
these
errors, and how easily can they recover from the errors?
o Satisfaction: How pleasant is it to use the design?
-
What is Usability???
-
Attributes of usability
-
User as starting point
-
Why usability is important?
o system development is expensive, and supporting a poorly
designed user interface is even more expensive;
o users will reject or work around systems that do not meet
their needs;
o design teams need to discover all problems users have in order
to provide remedies;
o even the best designers are not representative of the users of
the system, thus teams need to understand users' perspectives and
experiences with other systems;
-
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;
-
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
-
Where?
o Usability testing can be done wherever it is
o in a real work setting
o or in a usability lab
-
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
-
How conducting usability evaluation?
Usability methods
Testing
Inspection
Inquiry
-Laboratory testing -Thinking aloud
-Heuristic Evaluation -Cognitive Walkthrough
-Focus Group -Questionnaires
-
Laboratory Testing
o Defined as any of those techniques in which users interact
systematically with a product or system under controlled
conditions, to perform a goal-oriented task in an applied
scenario, and some behavioral data are collected.
o User is asked to perform task scenario based testing
-
Thinking aloud
o May be the single most valuable usability engineering
method.
o having an end user continuously thinking out loud while
using
the system
o participants thinking aloud as they are performing a set
of
specified tasks
o users are usually recorded on video
-
Thinking aloud
-
Focus Group
-
Planning a usability testing
o Think about why you will be doing a usability test.
o Consider the system as a whole.
o Make sure the system is ready to test.
o List several tasks that a user should be able to accomplish
with the system.
o Make a list of potential usability test subjects.
o Plan for data collection.
o Schedule the test.
o Prepare yourself to be objective.
o Don't take this "how" file with you.
-
Principles in testing
o Use real users
o Design real tasks
o Record and report the test
-
Who are the subjects tested?
o Targeted users
o Use a real user!!!
o Novice (beginner) vs expert user
o User persona
-
Between-subject & the Within-Subject Designs
Types of gathered users The between-subject design
The within-subject design Advantages Cleaner Smaller sample
size
Avoiding the learning effect
Effective isolation of individual differences
Better control of confounding factors, such as fatigue
More powerful tests
Limitations Larger sample size Hard to control learning
effects
Large impact of individual differences
Large impact of fatigue
Harder to get statistically significant results
Source: Lazar et.al (2009)
-
Get to know your users
o Talk to your users
o Observe your users
o Get feedback from your users
o Find out o Who are your users (characteristics)
o What do they do (tasks)
o Current vs. desired
o Critical vs. non-critical
o User/task matrix
o How do they do it (Task Flow)
o Where do they do it (environment)
-
How many subjects?
-
How many subjects?
-
Setting up usability testing
-
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
-
Measuring usability Effectiveness Efficiency User
satisfaction
1. Percent task complete
2. Ratio of success to
failures
3. Number of features
used
1. Time to complete task
2. Time to learn
3. Time spent on errors
1. Rating scale for
usefulness
2. Rating scale for
satisfaction
3. Number of times user
express frustration
-
Measuring Usability o Time
o 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:
-
Measuring Usability
o Error Rate o 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 Measures o attitude of the user of a system usually
has to be found by
using questionnaires or interviews. These measures can
cover complete system use, from learnability, to ease of
use, to functionality.
-
Measuring Usability
-
In usability testing
o Establish the context
o Ask the subject to verbalize their thoughts as they perform
the
tasks on your list
o Don't help!
o Don't take it personally
o Thank the subject.
-
Listen and observe!
o Have fun with it!
o Enjoy being the observer.
o What does "hmm" mean?
o Take it all in, even the gaps. Notice all the sounds and
behaviors and comments that might be relevant. Remind the subject
to verbalize and be as open with their thinking as possible.
o Write everything down.
o You can translate and expand your notes later. If you are
tempted to ask the subject extra questions, make a note so that you
can bring them up later.
o Don't interfere or ask leading questions
o Do help them to feel comfortable speaking their thoughts out
loud
-
Usability Applies to all Designs
o Norman presented
Carelmans coffeepot as a
metaphor for the
many objects that
we use in our daily
lives that include
fundamental design
flaws.
-
Referensi o ISO. 9241-11: 1998. (1998). Ergonomic
requirements
for office work with visual display terminals (VDTs)-
Part 11: guidance on usability. Geneve, CH: ISO
o Lazar, J., Feng, J. H., and Hochheiser, H. (2009).
Research methods in human-computer interaction.
John Wiley and Sons Inc.
o Nielsen, J. (1993) Usability engineering. Morgan
Kaufmann
o Wijayanto, T. (2009). Usability. Lecture Handout:
Usabilitas. Universitas Gajah Mada: Yogyakarta
