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CMC/CC A Usability Evaluation

CMC/CC A Usability Evaluation. Master IK, CIW, MMI L.M. Bosveld-de Smet Course 4; mon. 02/10/06; 16.00-18.00. Usability Evaluation. Design of interaction Dix et al. (2004). What is wanted. Analysis. Design. Usability Evaluation. Implement and deploy. Prototype.

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CMC/CC A Usability Evaluation

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  1. CMC/CC AUsability Evaluation Master IK, CIW, MMI L.M. Bosveld-de Smet Course 4; mon. 02/10/06; 16.00-18.00

  2. Usability Evaluation

  3. Design of interactionDix et al. (2004) What is wanted Analysis Design Usability Evaluation Implement and deploy Prototype

  4. Design process of usable interactive systems • Interaction design process • Complex • Iterative • Never complete • User-centered design • Within software engineering framework • Design rules • Implementation support • Evaluation techniques • Universally accessible designs • Provision of user support

  5. 3 related concepts • Usability: measure of success of a product • User-Centered Design: design involving user participation • Usability Engineering: • Whole process ensuring usable interactive systems • Process aiming at systems fit for the user, the task, the environment • Process implying user participation during software development • Process committing itself to design-evaluate-redesign development cycle • In search for objective measures for user interface

  6. Usability: different views • Same intuitions vs. Different approaches • Different views on: • Definition of usability • Usability attributes • Importance of user-centered design • When and how to deal with user participation • How to build usable systems • How to measure usability

  7. Usability Attributes: Shackel’s view • “A usable product is one that users find satisfactory for the tasks for which it was designed.” • “Good design for usability depends upon achieving successful harmony in the dynamic interplay between user, task, system, and environment.” • Usability: 4 usable criteria • Learnability • Effectiveness • Attitude • Flexibility

  8. Usability Attributes: ISO definition • “Usability is the effectiveness, efficiency and satisfaction with which specified users can achieve specified goals in particular environments.” • Effectiveness: “accuracy and completeness with which users achieve specific goals” • Efficiency: “accuracy and completeness of goals in relation to resources expended” • Satisfaction: “comfort and acceptability of the system”

  9. An aside: User Interface Standards • Disadvantages: • Constrain design • Stagnate innovation • Describe principles, do not provide solutions • Become quickly obsolete • Advantages: • Define ‘good practice’ • Affect attitudes w.r.t. ‘software development’

  10. User-Centered Design: Karat’s view • Karat (1996) “UCD: Quality or Quackery?” • “UCD is an iterative process whose goal is the development of usable systems, achieved through involvement of potential users of a system in system design” • “I suggest we consider UCD a nice fluffy little catch phrase. It captures a commitment that the usability community supports – that you must involve users in system design – while leaving fairly open how this is accomplished”

  11. UCD: a more objective view • UCD can be accomplished through the application of Usability Engineering • Design should centre on users • End-user should be consulted • Needs of end-users should be considered

  12. HCI in software process • Software engineering • Usability engineering • Iterative design practices • Design rationale

  13. Waterfall model Requirements Specification Architectural design Detailed Design Implementation and Unit testing Integration and Testing Operation and Maintenance

  14. Usability Engineering • Usability specification as part of requirements specification • Iteration and testing • List of usability measurement requirements (Whiteside, Bennett and Holtzblatt, 1988) • Time to complete a task • Ratio of successes to failures • Time spent in errors • Number of commands used • Frequency of help and documentation use • …

  15. Iteration in waterfall model Requirements Specification Architectural design Detailed Design Implementation and Unit testing Integration and Testing Operation and Maintenance

  16. Usability Engineering LifecycleFaulkner (2000) • Know the user • Know the task • User requirements capture • Setting usability goals • Design process • Apply guidelines, heuristics • Prototyping • Evaluation with users • Redesign and evaluation with users • Evaluation with users and report

  17. Role of prototyping Design OK? Prototype Evaluate Done! Not OK? Redesign

  18. Iterative design and prototyping • Three main approaches to prototyping • Throw-away prototyping within requirements specification • Incremental prototyping within the life cycle • Evolutionary prototyping throughout the life cycle

  19. Throw-away prototyping Preliminary Requirements Build Prototype Evaluate Prototype Adequate? no Final Requirements yes

  20. Evolutionary prototyping Req Build Prototype Arch Det Evaluate Prototype Impl Int Operation and Maintenance

  21. Usability Evaluation (UE) • Methodologies for measuring usability aspects of system’s user interface and identifying specific problems (Dix et al. 1998; Nielsen 1993) • Should occur throughout design life cycle • Common activities: • Capture • Analysis • Critic • There is a wide range of UE techniques • Each technique has its own requirements • Different techniques uncover different usability problems

  22. Taxonomies of UE (1) • Formative vs. Summative • Analytical vs. Empirical • Expert analysis vs. User participation • Analytic methods • Review methods • Model-based methods vs. • Experimental methods • Observational methods • Query methods

  23. Taxonomies of UE (2) • Automated vs. Non-automated • Ivory and Hearst (2001): • Testing • Inspection • Inquiry • Analytical modeling • Simulation

  24. Expert Analysis

  25. Controlled Experiment

  26. User participation

  27. Important factors choice UE • Stage in cycle at which UE is carried out • Style of UE • Level of subjectivity or objectivity of UE technique • Type of measures provided • Information provided • Immediacy of response • Level of interference implied • Resources required

  28. Analytic UE techniques

  29. Experimental and query UE techniques

  30. Observational UE techniques

  31. Monitoring UE techniques

  32. Vocabulary application • Task analysis • Feasability study • Design representation

  33. Feasibility study • Why is system needed? • How will system help to improve user task performance? • Are there critical processes that need to be supported by system? • What are the technical implications? • Can system be produced within given budget? • Is there a timescale for the development of the system?

  34. Strategies for representing design • Storyboards • State transition diagrams • Simulations • Scenarios • Rapid prototyping • Wizard of Oz • …

  35. Storyboard

  36. State Transition Diagram

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