Usability Testing

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

2. Contents • Introduction • Usability measurement • Data-collection techniques • 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. User need ident. Prototyping Evaluation UCD and Waterfall

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 communicateresults • 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 Usefullness Learnability Effectivity Satisfaction Memorability

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

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