Usability Goals
Setting
Chapter 04
Usability Engineering Life Cycle by
Deborah J. Mayhew
Usability Goal Setting
• It is universally understood in the engineering
discipline that to reach a satisfactory end
result on any engineering project, the project
team must establish and agree upon clear
goals and then work towards accomplishing
them.
• Designing without clear goal in mind is
“making a blind choice”
• Usability goals are mainly based on the User
Profile and the Contextual Task Analysis
• Categories of Usability Goals
– Qualitative Goals
– Quantitative Goals
Qualitative Usability Goals
• The general goals that guide design, which are
not quantified, for example
– The design must support users working in a high-
interrupt environment, with lots of context
information on screen to remind users where they
are when they get distracted
– The design must support very infrequent users of a
very complex task. Thus, it must be self-explanatory
and easy to learn and remember.
Quantitative Usability Goals
• Quantitative goals are objective and
measurable.
• These goals can serve as acceptance criteria
during usability evaluation
• Examples are
– Experienced user (defined as users who have performed
the transaction five times in a training session) should
take no longer than two minutes on average to
transcribe data from a certain paper form to a
certain on-line data entry form.
– Novice users (defined as first time users) should take
no longer than three minutes to fill in a certain on-
line subscription form
Classification of Quantitative
goals
• Ease-of-use goals
– Focus on the use of the product by experienced users
who have been trained on how to use the product
– Generally defined as the potential speed, efficiency
and flexibility an interface offers to an experienced
user
• Ease-of-learning goals
– Focus on the use of the product by first-time users or
infrequent users
• All quantitative usability goals can be
formulated as either absolute goals or relative
goals
Continue…
• Absolute Goals
– Those goals that have an absolute quantification, for
example, a specific number of seconds or minutes
per task or a specific number of errors per task or
transaction
• Relative Goals
– Refer to users’ experience on the product under
design relative to their experience on some
benchmark.
– E.g. experienced users should take less time on
average transcribing data from a certain paper form
to a certain on-line data entry form on release 2 as
compared to release 1
Continue..
• All quantitative usability goals can be formulated as
either performance goals or preference or satisfaction
goals
• Performance Goals
– Quantify actual user performance while using a product to
perform a task.
– The usual measure are time to complete a task and errors
(both number and task)
– No. of errors per unit time
– Number of navigation to online help or manuals
• Preference Goals
– A clear user preference among alternative interface based
on some level of experience
– Easily quantifiable; the user make a choice
• Satisfaction Goals
– A certain level of satisfaction with a particular interface
– These types of goals measure subjective reaction rather
than objective performance.
– Satisfaction can be measured along a scale, for example, a
5-points scale ranging from “Very unsatisfied” to
“Extremely Satisfied”
Sample work product and
templates
1. Qualitative Goals
2. Quantitative Goals
1.
2
End of the Lecture
