User Interface Design

1. IAT 334
Experimental Evaluation
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SCHOOL OF INTERACTIVE ARTS + TECHNOLOGY [SIAT] | WWW.SIAT.SFU.CA

2. March 10, 2011 IAT 334 2
Evaluation
 Evaluation styles
 Subjective data
– Questionnaires, Interviews
 Objective data
– Observing Users
• Techniques, Recording
 Usability Specifications
– Why, How

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Our goal?

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Evaluation
 Earlier:
– Interpretive and Predictive
• Heuristic evaluation, walkthroughs, ethnography…
 Now:
– User involved
• Usage observations, experiments, interviews...

5. March 10, 2011 IAT 334 5
Evaluation Forms
 Summative
– After a system has been finished. Make
judgments about final item.
 Formative
– As project is forming. All through the
lifecycle. Early, continuous.

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Evaluation Data Gathering
 Design the experiment to collect the data
to test the hypothesis to evaluate the
interface to refine the design
 Information we gather about an interface can
be subjective or objective
 Information also can be qualitative or
quantitative
– Which are tougher to measure?

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Subjective Data
 Satisfaction is an important factor in
performance over time
 Learning what people prefer is valuable
data to gather

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Methods
 Ways of gathering subjective data
– Questionnaires
– Interviews
– Booths (eg, trade show)
– Call-in product hot-line
– Field support workers

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Questionnaires
 Preparation is expensive, but
administration is cheap
 Oral vs. written
– Oral advs: Can ask follow-up questions
– Oral disadvs: Costly, time-consuming
 Forms can provide better quantitative
data

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Questionnaires
 Issues
– Only as good as questions you ask
– Establish purpose of questionnaire
– Don’t ask things that you will not use
– Who is your audience?
– How do you deliver and collect questionnaire?

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Questionnaire Topic
 Can gather demographic data and data
about the interface being studied
 Demographic data:
– Age, gender
– Task expertise
– Motivation
– Frequency of use
– Education/literacy

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Interface Data
 Can gather data about
– screen
– graphic design
– terminology
– capabilities
– learning
– overall impression
– ...

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Question Format
 Closed format
– Answer restricted to a set of choices
Characters on screen
hard to read easy to read
1 2 3 4 5 6 7

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Closed Format
 Likert Scale
– Typical scale uses 5, 7 or 9 choices
– Above that is hard to discern
– Doing an odd number gives the neutral
choice in the middle

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Closed Format
 Advantages
– Clarify alternatives
– Easily quantifiable
– Eliminates useless
answers
 Disadvantages
– Must cover whole
range
– All should be equally
likely
– Don’t get interesting,
“different” reactions

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Issues
 Question specificity
– “Do you have a computer?”
 Language
– Beware terminology, jargon
 Clarity
 Leading questions
– Can be phrased either positive or negative

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Issues
 Prestige bias
– People answer a certain way because they
want you to think that way about them
 Embarrassing questions
 Hypothetical questions
 “Halo effect”
– When estimate of one feature affects
estimate of another (eg, intelligence/looks)

18. March 10, 2011 IAT 334 18
Deployment
 Steps
– Discuss questions among team
– Administer verbally/written to a few people
(pilot). Verbally query about thoughts on
questions
– Administer final test

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Open-ended Questions
 Asks for unprompted opinions
 Good for general, subjective information,
but difficult to analyze rigorously
 May help with design ideas
– “Can you suggest improvements to this
interface?”

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Ethics
 People can be sensitive about this process and
issues
 Make sure they know you are testing
software, not them
 Attribution theory
– Studies why people believe that they succeeded or
failed--themselves or outside factors (gender, age
differences)
 Can quit anytime

21. March 10, 2011 IAT 334 21
Objective Data
 Users interact with interface
– You observe, monitor, calculate, examine,
measure, …
 Objective, scientific data gathering
 Comparison to interpretive/predictive
evaluation

22. March 10, 2011 IAT 334 22
Observing Users
 Not as easy as you think
 One of the best ways to gather feedback
about your interface
 Watch, listen and learn as a person
interacts with your system

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Observation
 Direct
– In same room
– Can be intrusive
– Users aware of your
presence
– Only see it one time
– May use
semitransparent mirror
to reduce
intrusiveness
 Indirect
– Video recording
– Reduces intrusiveness,
but doesn’t eliminate it
– Cameras focused on
screen, face &
keyboard
– Gives archival record,
but can spend a lot of
time reviewing it

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Location
 Observations may be
– In lab - Maybe a specially built usability lab
• Easier to control
• Can have user complete set of tasks
– In field
• Watch their everyday actions
• More realistic
• Harder to control other factors

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Challenge
 In simple observation, you observe
actions but don’t know what’s going on in
their head
 Often utilize some form of verbal protocol
where users describe their thoughts

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Verbal Protocol
 One technique: Think-aloud
– User describes verbally what s/he is thinking
and doing
• What they believe is happening
• Why they take an action
• What they are trying to do

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Think Aloud
 Very widely used, useful technique
 Allows you to understand user’s thought
processes better
 Potential problems:
– Can be awkward for participant
– Thinking aloud can modify way user performs
task

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Teams
 Another technique: Co-discovery learning
– Join pairs of participants to work together
– Use think aloud
– Perhaps have one person be semi-expert
(coach) and one be novice
– More natural (like conversation) so removes
some awkwardness of individual think aloud

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Alternative
 What if thinking aloud during session will
be too disruptive?
 Can use post-event protocol
– User performs session, then watches video
afterwards and describes what s/he was
thinking
– Sometimes difficult to recall

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Historical Record
 In observing users, how do you capture
events in the session for later analysis?

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Capturing a Session
 1. Paper & pencil
– Can be slow
– May miss things
– Is definitely cheap and easy
Time 10:00
10:03
10:08
10:22
Task 1 Task 2 Task 3 …
S
e
S
e

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Capturing a Session
 2. Audio tape
– Good for talk-aloud
– Hard to tie to interface
 3. Video tape
– Multiple cameras probably needed
– Good record
– Can be intrusive

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Capturing a Session
 4. Software logging
– Modify software to log user actions
– Can give time-stamped key press or mouse
event
– Two problems:
• Too low-level, want higher level events
• Massive amount of data, need analysis tools

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Assessing Usability
 Usability Specifications
– Quantitative usability goals, used a guide for
knowing when interface is “good enough”
– Should be established as early as possible in
development process

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Measurement Process
 “If you can’t measure it, you can’t
manage it”
 Need to keep gathering data on each
iterative refinement

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What to Measure?
 Usability attributes
– Initial performance
– Long-term performance
– Learnability
– Retainability
– Advanced feature usage
– First impression
– Long-term user satisfaction

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How to Measure?
 Benchmark Task
– Specific, clearly stated task for users to carry
out
 Example: Calendar manager
– “Schedule an appointment with Prof. Smith
for next Thursday at 3pm.”
 Users perform these under a variety of
conditions and you measure performance

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Assessment Technique
Usability Measure Value to Current Worst Planned Best poss Observ
attribute instrument be measured level acc level target level level results
Initial Benchmk Length of 15 secs 30 secs 20 secs 10 secs
perf task time to (manual)
success add
appt on
first trial
First Quest -2..2 ?? 0 0.75 1.5
impression

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Summary
 Measuring Instrument
– Questionnaires
– Benchmark tasks

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Summary
 Value to be measured
– Time to complete task
– Number of percentage of errors
– Percent of task completed in given time
– Ratio of successes to failures
– Number of commands used
– Frequency of help usage

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Summary
 Target level
– Often established by comparison with
competing system or non-computer based
task

42. Ethics
 Testing can be arduous
 Each participant should consent to be in
experiment (informal or formal)
– Know what experiment involves, what to
expect, what the potential risks are
 Must be able to stop without danger or
penalty
 All participants to be treated with respect
Nov 2, 2009 IAT 334 42

43. Consent
 Why important?
– People can be sensitive about this process and issues
– Errors will likely be made, participant may feel
inadequate
– May be mentally or physically strenuous
 What are the potential risks (there are always
risks)?
– Examples?
 “Vulnerable” populations need special care &
consideration (& IRB review)
– Children; disabled; pregnant; students (why?)
Nov 2, 2009 IAT 334 43

44. Before Study
 Be well prepared so participant’s time is not
wasted
 Make sure they know you are testing software,
not them
– (Usability testing, not User testing)
 Maintain privacy
 Explain procedures without compromising
results
 Can quit anytime
 Administer signed consent form
Nov 2, 2009 IAT 334 44

45. During Study
 Make sure participant is comfortable
 Session should not be too long
 Maintain relaxed atmosphere
 Never indicate displeasure or anger
Nov 2, 2009 IAT 334 45

46. After Study
 State how session will help you improve system
 Show participant how to perform failed tasks
 Don’t compromise privacy (never identify
people, only show videos with explicit
permission)
 Data to be stored anonymously, securely,
and/or destroyed
Nov 2, 2009 IAT 334 46

47. March 10, 2011 IAT 334 47
One Model