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Usability Engineering

Usability Engineering. Dr. Dania Bilal IS 582 Spring 2007. Usability Engineering?. Measures multiple components of the user interface Addresses the relationships between system and its users Focuses on the HCI field. What Is Usability Engineering?.

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Usability Engineering

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  1. Usability Engineering Dr. Dania Bilal IS 582 Spring 2007

  2. Usability Engineering? • Measures multiple components of the user interface • Addresses the relationships between system and its users • Focuses on the HCI field

  3. What Is Usability Engineering? • Bridges the gap between human and machines • Measures the quality of a system in relation to its intended users • Involves several methods, each applied at appropriate time of the design and development process

  4. Importance of Usability • The sooner problems are found, the less expensive it is to fix them • Saves money by reducing designers’ time • Provides information about user experience • Cognitive, affective, and psychomotor • Depends on method(s) employed

  5. Importance of Usability • Learn more about users, tasks, expectations, successes, failures, information seeking, etc. and take these into consideration in redesigning a system or designing new one

  6. Usability Attributes • As described by Neilsen • Learnability • Efficiency • Memorability • Errors & their severity • Subjective satisfaction

  7. Learnability • System must be easy to learn, especially for novice users • Hard to learn • systems are usually designed for expert users • Learning curve for novice and expert users

  8. Efficiency • System should be efficient to use so that once the user has learned how to use it, the user can achieve a high level of productivity • Efficiency increases with learning

  9. Memorability • System should be easy to remember, especially by casual users • No need to learn how to use system all over again after a period of not using it

  10. Errors • System should have a low error rate • System should provide user with a recovery mechanism • Minor errors • Major errors

  11. Minor Errors • Errors that did not greatly slow down user’s interaction with the system • User is able to recover from them • through system feedback • through awareness of error made

  12. Major Errors • Difficult to recover from them • Lead to faulty work if high in frequency • May not be discovered by the user • Errors can be catastrophic

  13. Subjective Satisfaction • System should be likeable by users (affective) • Satisfaction varies with purpose of system • Educational vs. entertainment

  14. Assumptions • The designer’s best guess is not good enough • The user is always right • The user is not always right • Users are not designers • Designers are not users • More features are not always better • Minor interface details matter • Online help does not really help Source: Nielsen, J. (1993). Usability Engineering. San Diego: Morgan Kaufman.

  15. Factors Influencing User Interaction • Address the functionality of the system vis-à-vis: • user needs • user tasks • user information seeking • user expectations • user cognitive processes

  16. Evaluation • Component of usability engineering • Involves users in the evaluation • Users perform tasks developed by evaluator • Main goal • Uncover problems and correct them

  17. Evaluation • Can be done before, during, and after system is designed and developed • Before design • During design • After release

  18. Usability Methods: Cognitive Walkthrough • Involves experts acting on behalf of actual users • Goal- and task- driven of how user approaches a task in a system • An observer “experimenter” is present • Prepares tasks • Takes notes • Provides help

  19. Usability Testing • Actual users interact with system • Users perform tasks assigned by evaluator • Users’ activities are captured • Methods • Users may also be interviewed • Captured data are coded, analyzed, and reported • Interview data are coded, analyzed, and reported

  20. Heuristic Evaluation • Evaluators interact with an interface several times and map interface to specific heuristics or guidelines • See Neilsen’s ten heuristics • Each evaluator generates a report • Reports are aggregated and final report is generated • An observer may be present

  21. Field Studies • Actual users • Users are observed in naturalistic setting • No tasks are assigned to users • Users’ interaction with system are captured, analyzed, interpreted, etc. • Interviews can be used in addition to observations

  22. Usability Heuristics • http://www.usabilityfirst.com/methods • http://www.useit.com/papers/heuristic/heuristic_list.html (Neilsen’s usability heuristics) • http://www.useit.com/papers/heuristic/heuristic_evaluation.html (how to conduct a heuristic evaluation) • http://www.uie.com/articles (collection of articles) • http://www.uie.com/articles/usability_tests_learn/ Learning about usability test (Jared Spool) • http://www.useit.com/papers/heuristic/severityrating.html (Severity rating)

  23. Usability Tests • Stages • Preparation • Introduction • User interaction and caputre • Debriefing Neilsen, J. (1993). Usability Engineering. San Diego: Morgan Kaufman.

  24. Preparation • Preparation for the experiment and data collection • Location of test (e.g., room to be used) • System to be used, capturing software, etc. • Test materials, instructions, questionnaires to be completed, as applicable

  25. Introduction • Purpose of the test • Results will be used to improve interface • User cnfidentiality & IRB • Software and equipment used to collect data

  26. Introduction • Users to ask questions before and during experiment • Type of questions accepted • Users to report problems and difficulty in using system (e.g., screen freeze) • May provide verbal instructions

  27. Running the Test • Experimenter(s) should refrain from interacting with users • Don’t give your personal opinion • Don’t tell user how to perform certain function • Don’t distract user during the interaction

  28. Debriefing • User is debriefed after the test • Experimenter may follow up with questions about interaction • Likes, dislikes, comments, suggestions for system improvements, etc. • Verbally (individual interview) • Structured or semi-structured • Questionnaire with both closed and open-ended questions

  29. Debriefing • Experimenter ensures that data collected from each user are labeled • User is given a code or number for identification purposes • Experimenter writes a brief preliminary report while events are still fresh • Collected data are coded, analyzed, interpreted, and reported

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