Guest * Posted June 10, 2002 Share Posted June 10, 2002 TASK 1 “Human-computer interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them.” [ACM SIGCHI Curricula for Human-Computer Interaction] EVALUATION OF EASYCAR WEB SITE How Many Potential Problems are there in the web site ? Help Users Recognize, Diagnose, and Recover from Errors 69. If a required field is empty (state without city, city without state) indicate the precise condition in the error message. 70. If all three input fields are non-empty, there should be an appropriate error message. 71. If the user enters an invalid syntax, the error message should indicate what input was received and make a constructive suggestion. 72. If the system discovers that a (syntactically valid) ZIP code does not exist, precisely this should be indicated. 73. If a state does not exist, precisely this should be indicated. 74. If a city does not exist in a state (New York, Florida), a list of states where it does exist should be output. 75. “Please try again” is meaningless. Help and Documentation 76. Provide links to further more detailed help. 77. Explain somewhere that large cities have multiple ZIP codes and that a single ZIP code sometimes covers several neighbouring districts or towns. 78. Explain somewhere the valid syntax and formats for ZIP code, city, and state. CONCLUSIONS Our suggestions At least 4 interfaces Principles for User-Centered Design 1. Explicit, coherent conceptual model. 2. Make things visible. 3. Get the mappings right. 4. Exploit the power of constraints. 5. Utilise platform standards and conventions. 6. Design for error, allowing exploration without penalty. “Usability: the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.”. [iSO 9241] Five Usability Attributes 1. Learnability: ease of learning for novice users. 2. Efficiency: steady-state performance of expert users. 3. Memorability: ease of using system intermittently for casual users. 4. Errors: error rate for minor and catastrophic errors. 5. Subjective Satisfaction: how pleasant system is to use. Typical Ways of Measuring Usability _ Learnability: pick novice users of system, measure time to perform certain tasks. Distinguish between no/some general computer experience. _ Efficiency: decide definition of expertise, get sample expert users (difficult), measure time to perform typical tasks. _ Memorability: get sample casual users (away from system for certain time), measure time to perform typical tasks. _ Errors: count minor and catastrophic errors made by users while performing some specified task. _ Satisfaction: ask users’ subjective opinion (questionnaire), after trying system for real task. Know the User _ Observe Users in Working Environment: Site visits, unobtrusive observation. Don’t believe their superiors! _ Individual User Characteristics: Classify users by experience, educational level, age, amount of prior training, etc. _ Task Analysis: Users’ overall goals, current approach, model of task, prerequisite information, exceptions to normal work flow. _ Functional Analysis: Functional reason for task: what really needs to be done, and what are merely surface procedures? Draw up a user profile for each (potential) class of user. Draw up set of typical user scenarios to set the scene for brainstorming, thinking aloud, or cognitive walkthrough, etc. TASK 2 4.2.5 Interactive Design “Design, Test, Redesign.” Build and evaluate prototype interface, then: _ Severity ratings of usability problems discovered. _ Fix problems!new version of interface. _ Capture design rationale: record reasons why changes were made. _ Evaluate new version of interface. until time and/or money runs out. Building Prototypes _ Verbal description. _ Paper prototype. _ Working prototype. _ Implementation of final design. See Chapter 6. Usability Evaluation _ Usability Inspection Inspection of interface design using heuristics and judgement (no user tests). See Chapter 7. _ Usability Testing Empirical testing of interface design with real users. See Chapter 8. TASK 3 3 The Psychology of Usable Things “Kenneth Olsen, the engineer who founded and still runs Digital Equipment Corp., confessed at the annual meeting that he can’t figure out how to heat a cup of coffee in the company’s microwave oven.” [Wall Street Journal, 1986] The Psychopathology of Everyday Things Examples of where the design of everyday things went wrong. The Frustrations of Everyday Life Can you use all the functions of your: _ digital watch? _ mobile phone? _ washing machine? _ video recorder? Some of the buttons on a VCR remote control are easy to understand, but others are unfathomable without the instruction manual. Real World Affordances For physical objects, there can be both real and perceived affordances (and the two sets are not necessarily the same). _ Appearance indicates how to use something: – A chair affords (suggests) sitting. – Knobs are for turning. – Slots are for inserting things. – A button affords pushing. _ When perceived affordances are taken advantage of, the user knows what to do just by looking. _ When simple things need pictures, labels, or instructions, the design has failed! GUI Affordances For screen-based interfaces, the computer hardware already has built-in physical affordances: _ Screen affords touching. _ Mouse affords pointing. _ Mouse buttons afford clicking. _ Keyboard affords typing. Changing the shape of the cursor to indicate a clickable link is not an affordance (you can still click anywhere), but visual feedback. Physically locking the mouse button on non-clickable areas is a real affordance. The Structure of Human Memory Short-Term Memory (STM) Short-term memory is the memory of the present, used as working or temporary memory. _ Information is retained in STM automatically and is retrieved without effort. _ However, the amount of information in STM is severely limited: 7 _ 2 items [Miller, 1956] _ STM is extremely fragile – the slightest distraction and its contents are gone. For example, STM can hold a seven digit phone number from the time you look it up until the time you use it, as long as no distractions occur. Long Term Memory (LTM) Long-term memory is the memory of the past. _ It takes time to put stuff into LTM and time and effort to get stuff out. _ Capacity is estimated at about 100 million items. To Err is Human _ People make errors routinely, you must design for error. _ Assume that any error, that can be made, will be made! _ Design explorable systems, where operations are easy to reverse. Categories of Error Two fundamental categories of error: _ Slips result from automatic behaviour, when subconscious actions toward a correct goal go wrong. _ Mistakes result from conscious deliberations, which formed an inappropriate goal. Quote Link to comment Share on other sites More sharing options...
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