Usability Testing

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Usability Testing

• HiØ, Masterstudium Informatikk
• Grensesnittdesign høsten 2006
• Gisle Andresen (gislea_at_hrp.no) Forsker,
  Institutt for Energiteknik

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Contents

• Introduction
• Usability measurement
• Data-collection techniques
• Evaluation of usability tests

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User-centered design

• A design approach driven by the needs and
  preferences of users in order to create effective
  interactive systems
• UCD ensures Usability

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Why UCD?

• Negative consequences of not following UCD poor
  usability
• reduced effectivity,
• human errors,
• frustration etc.

http//www.usabilitymustdie.com/usability_review_r
emote_control.htm
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Why UCD?

• Positive consequences of following UCD approach
  good usability
• increased effectivity,
• Error tolerance,
• User satisfaction etc.

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Why UCD?

• A reaction against technology- centered design
  i.e., design driven by what is technologically
  possible
• left-over principle we automate everything
  possible and leave the rest to the human

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Key activities of UCD process

• Identify user needs
• Develop prototypes
• Perform usability evaluations

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Typical project model Waterfall
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UCD and Waterfall
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Usability evaluations

• Inspection
• Usability testing

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Usability testing characteristics

• Several real users participate
• The users performs realistic tasks
• Measure usability
• Use/Problem descriptions

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Why several real users?

• Users differ from designers
• Users differ from one another

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Why realistic tasks?

• Find usability problems of significance to task
  performance

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Why measure?

• Scientific reasons
• Pragmatic reasons

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Scientic reasons

• Everything
• that exists,
• exists in some
• amount

http//serendip.brynmawr.edu/exhibitions/Mind/Imag
es/42.GIF
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Pragmatic reasons

• Define specific goals
• Easy to communicateresults
• Allows statistical analysis
• High status

http//www.usabilitymustdie.com/askJakob.htm
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Why Use-/problem descriptions?

• Learn how the system is really used
• Find causes of usability problems

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Usability testing approaches (Preece)

• Formative vs. Summative
• Quick and dirty vs. Experimental

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Usability testing approaches (Rubin)

• Exploratory test
• Assessment test
• Validation test
• Comparison test

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What determines the approach?

• Purpose of test
• Stage in the design process
• Practical limitations

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Usability measures

• Measure
• to assign numbers
• to objects or attributes according to rules

http//www.psych.utoronto.ca/museum/hippchron.htm
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Creating a usability measure

• Select usability attribute
• Operationalise criteria
• Select data-collection technique

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Usability attributes
Efficiency
Usefullness
Learnability
Effectivity
Satisfaction
Memorability
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Select attribute

• What attributes are most relevant?
• Important to take into account characteristics of
  the users, tasks and context

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Select attribute Examples

• Commercial easy to learn
• Entertainment satisfaction
• Seldom used memorability
• Innovative usefullness
• Safety relevant effective
• Complex efficient

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Operationalise criteria

• Can the attribute be measured?
• Define a scale
• Define acceptance or target criteria

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Operationalise criteria Example 1

• Effective
• Number of tasks performed correctly
• Scale Summarise the number of tasks performed
  and divide by number of possible tasks
• Criteria All users must perform all important
  tasks

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Operationalise criteria Example 2

• Efficient
• The effort users have to invest in performing the
  task
• Scale the more effort, the less efficient
• Criteria less effort than old product

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Operationalise criteria Example 3
http//zing.ncsl.nist.gov/hfweb/proceedings/etgen-
cantor/
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Student tasks

• Can you think of any potential usability problems
  with your product?
• What is the most important usability attribute
  for your product?