![IAT 334
Experimental Evaluation
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IAT334-Lec08-Experiment.pptx
- 1. IAT 334 Experimental Evaluation ______________________________________________________________________________________ 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
- 3. March 10, 2011 IAT 334 3 Our goal?
- 4. March 10, 2011 IAT 334 4 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.
- 6. March 10, 2011 IAT 334 6 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?
- 7. March 10, 2011 IAT 334 7 Subjective Data Satisfaction is an important factor in performance over time Learning what people prefer is valuable data to gather
- 8. March 10, 2011 IAT 334 8 Methods Ways of gathering subjective data – Questionnaires – Interviews – Booths (eg, trade show) – Call-in product hot-line – Field support workers
- 9. March 10, 2011 IAT 334 9 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
- 10. March 10, 2011 IAT 334 10 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?
- 11. March 10, 2011 IAT 334 11 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
- 12. March 10, 2011 IAT 334 12 Interface Data Can gather data about – screen – graphic design – terminology – capabilities – learning – overall impression – ...
- 13. March 10, 2011 IAT 334 13 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
- 14. March 10, 2011 IAT 334 14 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
- 15. March 10, 2011 IAT 334 15 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
- 16. March 10, 2011 IAT 334 16 Issues Question specificity – “Do you have a computer?” Language – Beware terminology, jargon Clarity Leading questions – Can be phrased either positive or negative
- 17. March 10, 2011 IAT 334 17 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
- 19. March 10, 2011 IAT 334 19 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?”
- 20. March 10, 2011 IAT 334 20 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
- 23. March 10, 2011 IAT 334 23 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
- 24. March 10, 2011 IAT 334 24 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
- 25. March 10, 2011 IAT 334 25 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
- 26. March 10, 2011 IAT 334 26 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
- 27. March 10, 2011 IAT 334 27 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
- 28. March 10, 2011 IAT 334 28 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
- 29. March 10, 2011 IAT 334 29 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
- 30. March 10, 2011 IAT 334 30 Historical Record In observing users, how do you capture events in the session for later analysis?
- 31. March 10, 2011 IAT 334 31 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
- 32. March 10, 2011 IAT 334 32 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
- 33. March 10, 2011 IAT 334 33 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
- 34. March 10, 2011 IAT 334 34 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
- 35. March 10, 2011 IAT 334 35 Measurement Process “If you can’t measure it, you can’t manage it” Need to keep gathering data on each iterative refinement
- 36. March 10, 2011 IAT 334 36 What to Measure? Usability attributes – Initial performance – Long-term performance – Learnability – Retainability – Advanced feature usage – First impression – Long-term user satisfaction
- 37. March 10, 2011 IAT 334 37 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
- 38. March 10, 2011 IAT 334 38 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
- 39. March 10, 2011 IAT 334 39 Summary Measuring Instrument – Questionnaires – Benchmark tasks
- 40. March 10, 2011 IAT 334 40 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
- 41. March 10, 2011 IAT 334 41 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