1. Usability Testing HiØ, Masterstudium Informatikk Grensesnittdesign høsten 2006 Gisle Andresen (gislea@hrp.no) Forsker, Institutt for Energiteknik

2. Contents 1. Introduction 2. Usability measurement 3. Data-collection techniques 4. Evaluation of usability tests

3. User-centered design A design approach driven by the needs and preferences of users in order to create effective interactive systems UCD ensures Usability

4. Why UCD? Negative consequences of not following UCD: poor usability reduced effectivity, human errors, frustration etc. http://www.usabilitymustdie.com/usability_review_remote_control.htm

5. Why UCD? Positive consequences of following UCD approach: good usability increased effectivity, Error tolerance, User satisfaction etc.

6. 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

7. Key activities of UCD process Identify user needs Develop prototypes Perform usability evaluations

8. Typical project model: Waterfall

9. UCD and Waterfall User need ident. PrototypingEvaluation

10. Usability evaluations Inspection Usability testing

11. Usability testing: characteristics Several ”real” users participate The users performs realistic tasks Measure usability Use/Problem descriptions

12. Why several real users? Users differ from designers Users differ from one another

13. Why realistic tasks? Find usability problems of significance to task performance

14. Why measure? Scientific reasons Pragmatic reasons

15. Scientic reasons Everything that exists, exists in some amount http://serendip.brynmawr.edu/exhibitions/Mind/Images/42.GIF

16. Pragmatic reasons Define specific goals Easy to communicate results Allows statistical analysis High status http://www.usabilitymustdie.com/askJakob.htm

17. Why Use-/problem descriptions? Learn how the system is really used Find causes of usability problems

18. Usability testing approaches (Preece) Formative vs. Summative Quick and dirty vs. Experimental

19. Usability testing approaches (Rubin) Exploratory test Assessment test Validation test Comparison test

20. What determines the approach? Purpose of test Stage in the design process Practical limitations

21. Usability measures Measure: to assign numbers to objects or attributes according to rules http://www.psych.utoronto.ca/museum/hippchron.htm

22. Creating a usability measure Select usability attribute Operationalise criteria Select data-collection technique

23. Usability attributes Efficiency Effectivity Satisfaction Learnability Memorability Usefullness

24. Select attribute What attributes are most relevant? Important to take into account characteristics of the users, tasks and context

25. Select attribute: Examples Commercial: easy to learn Entertainment: satisfaction Seldom used: memorability Innovative: usefullness Safety relevant: effective Complex: efficient

26. Operationalise criteria Can the attribute be ”measured”? Define a scale Define acceptance or target criteria

27. 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

28. 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

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

30. Student tasks Can you think of any potential usability problems with your product? What is the most important usability attribute for your product?