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Usability testing

Usability testing






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    Usability testing Usability testing Presentation Transcript

    • Usability Testing Chapter 6
    • Reliability
      • Can you repeat the test?
    • Reliability
      • Huge difference between test subjects
        • Therefore, only 2 subjects is not a good reliability check
      • Significance levels (e.g., p = .20)
      • Confidence levels
        • When should an usability problem be fixed?
      • Error rates have the highest variability
        • Therefore, more test subjects are needed
    • Validity
      • Does this test reflect what usability issues you want to test?
      • Reliability measured with stats but validity requires methodological understanding
      • Typical problems
        • Wrong users or wrong tasks
        • Confounding effects – text based to GUI system
    • Test Plans
      • What’s the goal of the test?
      • What is it you are trying to prove or show?
      • Pilot tests – show the problem areas of the test. E.g., the instructions
    • Test Plans
      • The goal of the test?
      • Where and were will the test take place?
      • How long is each test session expected to take?
      • What computer support will be needed for the test?
      • What software needs to be ready for the test?
      • Who will serve as experimenters for the test?
      • How many test users are needed?
    • Getting Test Users
      • Test subjects (users) should be representative of who will use the system.
      • Sales (“demoability”) – is it easy to show
      • Asking managers to choose subjects
        • They will pick the best or the worse
      • Formative evaluation
        • Help improve the interface as part of an iterative design process
      • Summative
        • Assessing the overall quality of an interface
    • Novice and expert users
      • Most tests should test novice users
      • If possible, test for expert users. But test separately from novice users.
      • What are the effects of training or not training before a test?
    • Between-Subject test
      • Simplest and most valid
      • Different tests subject using different systems
      • Possible problems:
        • Individual differences
        • Assignment to test groups (volunteer early or late)
    • Within-Subject test
      • All users are tested on all systems
      • Problem: no longer a set of novice users when testing a secondary system
    • Choosing experimenters
      • It’s better to get an usability person to conduct the test but you, the developer, can also run a test
      • In fact, it’s good to know the system well
      • From Usability Engineering (Nielsen)
        • “ It is possible for computer scientistws to learn user test methods and apply them with good results.”
      • However, designers try to explain away problems.
    • Ethical aspect of testing human beings
      • Users should feel as comfortable as possible
      • Tell the test subjects:
        • No information will be revealed
        • Explain the testing environment. E.g., computer, etc.
      • The tester should not allow observers because they tend to influence results.
      • The tester should not interfere with the user. Let the user find the solution themselves
      • Emphasize that it is the system that is being tested, not the user
    • Test tasks
      • Based on a task analysis. What is it the user needs to do.
      • Tasks should be small enough to be completed in time that the experiment takes.
      • Test tasks should be in writing. The user may refer to the steps.
    • Stages of a Test
      • 1. Prep – is everything in working order?
      • 2. Intro - tell the user the purpose of the test.
      • 3. Test
      • 4. Debrief
    • Stages of a Test
      • Intro - tell the user the purpose of the test.
      • A reminder that the test is confidential and should not be discussed with others
      • A statement that participation is the test is voluntary and the user may stop at any time
      • At FIT a human test subject document needs to be signed by the tester and returned to the university.
    • Performance Measurement
      • Has the usability goals been met? (see page 194)
      • Test a set of tasks
      • The data collected: time to perform and error rate
      • Goals are abstract, so break them down.
      • Make sure you know the start and finish of a measured test
    • Thinking aloud
      • “ verbalizing their thoughts”
      • Shows how users interpret each interface item
      • Users performed 9 % better using thinking aloud.
      • Constructive interaction (co-discovery learning) and coaching methods.
    • Usability Labs
      • Is there really a need?
      • Why videotape? Impact analysis – you look after taping for a known problem.
      • Convince the manager and developers
      • Usability kiosks