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User Interfaces

User Interfaces

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User Interfaces

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  1. User Interfaces CS 414, Software Engineering I Mark Ardis Rose-Hulman Institute December 10, 2002

  2. Outline • Psychology of interfaces • Task analysis • User interface testing methods • Measurement techniques

  3. User Interface Spiral Evaluation Analysis Design Implementation

  4. Psychology and Design • Understand human side of interfaces • Perception • Attention • Performance • Memory

  5. HumanInformationProcessor OutputDevices InputDevices Computer Human and the Machine

  6. Long Term Memory Short Term Memory Short TermSensory Store Effectors Sensors Eyes Fingers Ears Human Information Processor elaboration retrieval attention performance

  7. Attention • Works as a filter for information • Affected by expectations • Multi-modal presentations allow more information processing

  8. Performance • Pointing (selecting) can be predicted by Fitts's Law • Practice leads to automatic behavior • need for attention drops • Action slips • caused by inattention

  9. Fitts's Law Movement Time = a + b ID ID = log2 ( 2A / W ) A = amplitude (size of movement) W = width of target ID is the index of difficulty a, b are constants

  10. Memory • Short Term Sensory Store - 100 msec • Short Term Memory - 15 sec 7  2 chunks • Long Term Memory • proactive interference • hard to learn a new system • retroactive interference • hard to return to an old system

  11. Working Memory • Users need to retain several different types of information in order to accomplish a task • There is a limit to amount of information that can be recalled easily • Designers need to break up complicated tasks into sequences of simpler tasks

  12. Conceptual Models • Abstraction of system • Simple enough for non-technical users • Often described by analogy • clipboard for copied text • folder for collection of files • Should be made explicit

  13. Outline • Psychology of interfaces • Task analysis • User interface testing methods • Measurement techniques

  14. Task Analysis • Observe users in their natural habitat • Interview users • Write down sequences of actions required to accomplish tasks • Refine and categorize actions

  15. Example Task Analysis Example: Correcting a manuscript • Find location of change • Scroll document • Move cursor • Delete old text • Insert new text

  16. Screen Layout • Collect a set of scenarios (use cases) • Describe each scenario with sequence of tasks from task analysis • Identify actions (verbs) and objects (nouns) • Draw screen layouts showing objects • Simulate actions

  17. Guidelines • Several good books available • Some guidelines in Pressman: • Place the user in control • Reduce the user's memory load • Make the interface consistent

  18. Place the User in Control • Provide for flexible interaction • Allow interruption and undo • Allow customization • User direct manipulation of screen objects

  19. Prototyping • Useful for creating screen layouts • Allows feedback from users • Provides starting point for User Manual

  20. Cartoon of the Day

  21. Outline • Psychology of interfaces • Task analysis • User interface testing methods • Measurement techniques

  22. UI Testing Methods • Experiments • Interviews • Observation • Heuristic evaluation • Focus groups • Input logging • Surveys

  23. Experiments • Useful for testing alternatives • Requires expert to construct • need to use appropriate experimental design • need to control variables • Used during design

  24. Interviews • Useful for collecting requirements and for spot-checking other results • Require planning • use a standard list of questions • allow open-ended questions • Analysis may be hard

  25. Observation • Useful for learning about "real environment" use • Should be planned • identify behaviors of interest • use multiple observers to categorize behaviors • May be intrusive or blind

  26. Heuristic Evaluation • Experts examine a product and produce scores for each principle of good design • Cheap and easy to perform • Biased by expert opinions

  27. Focus Groups • Moderated interview of several potential users (1-2 hours) • Useful when product is unavailable, or its use is uncommon • Moderator presents scenarios, or descriptions of a product, or only a concept

  28. Input Logging • Instrumentation used to collect data from use • Many types of measurements: • frequency • time • errors

  29. Surveys • Useful for longitudinal studies • Depends on accuracy of sampling • volunteer surveys tend to be more positive than general population • rewards may be used to encourage participation • Good method for collecting attitudinal data

  30. Users Needed • Experiments: > 10 • Interviews: 5-10 • Observation: 3-5 • Heuristic evaluation: 0 (need experts) • Focus groups: 6-9/group • Input logging: > 20 • Surveys: 100s

  31. Outline • Psychology of interfaces • Task analysis • User interface testing methods • Measurement techniques

  32. Measurement Techniques • Questionnaires • Performance measures • Thinking aloud • Audio-video recording

  33. Questionnaires • Cheap to implement, may be reused • Require careful design • need to be of appropriate length • need to calibrate scales • may duplicate questions to check validity • Useful for surveys, experiments and interviews

  34. Performance Measures • Objective measures • reaction time • accuracy • frequency • Useful for input logging and experiments

  35. Thinking Aloud • Subject thinks out loud while using product • May also be done as a coaching session • Useful for experiments and interviews

  36. Audio-video Recording • Videotape user in action • Collects a lot of important information • May collect too much information • Useful for experiments and observation

  37. Good and Bad Examples Yale Web Style Guide: http://info.med.yale.edu/caim/manual Interface Hall of Shame: http://www.iarchitect.com/mshame.htm

  38. Quiz!