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Course Introduction; Principles of Good Design

Course Introduction; Principles of Good Design. Professor Larry Heimann Carnegie Mellon University 88-272 Lecture Notes — Fall 1999. Agenda. Course Introduction & Overview The Problems of Design The Psychology of Users Principles for User-Centered Design Why Designers Go Astray.

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Course Introduction; Principles of Good Design

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  1. Course Introduction;Principles of Good Design Professor Larry Heimann Carnegie Mellon University 88-272 Lecture Notes — Fall 1999

  2. Agenda • Course Introduction & Overview • The Problems of Design • The Psychology of Users • Principles for User-Centered Design • Why Designers Go Astray

  3. Course Business • Welcome to 88-272 • Introduction of Professors • Professor Peter Muhlberger • Professor Larry Heimann • Course Policies • complete listing of course policies at website • http://www.andrew.cmu.edu/course/88-272/index.html • print out syllabus and first lab instructional material

  4. Course Expectations & Overview • Course Expectations • What is this course supposed to be? • What this course is not supposed to be • Course Overview • Begin with design and interface issues • Spend time on database issues and SQL • Move to web development via ASP and CGI • Return to usability and software processes

  5. The Problems of Design • The frustration of everyday life • my problems using our cordless phone • using my digital watch as a stop watch • opening doors • The need for good conceptual models • my solution to the door opening problem • example of freezer/refrigerator

  6. Freezer/Refrigerator Controls NORMAL SETTING C AND 5 COLDER FRESH FOOD C AND 6-7 COLDEST FRESH FOOD B AND 8-9 COLDER FREEZER D AND 7-8 WARMER FRESH FOOD C AND 4-1 OFF (FRESH FD & FRZ) 0 1 SET BOTH CONTROLS 2 ALLOW 24 HOURS TO STABILIZE A B C D E 7 6 5 4 3 FREEZER FRESH FOOD

  7. A Conceptual Model of F/R Freezer (w/ thermostat) Fresh Food (w/ thermostat) Freezer Control Fresh FD Control Cooling Unit Cooling Unit

  8. Correct Conceptual Model of F/R Thermostat Control A Freezer Cooling Unit COLD AIR Fresh Food Control B

  9. The Problems of Design • The frustration of everyday life • my problems with using our cordless phone • using my digital watch as a stop watch • opening doors • The need for good conceptual models • my solution to the door opening problem • example of freezer/refrigerator • conceptual models guide user actions; wrong conceptual models leads to inexplicable errors

  10. Design Problems… (continued) • The principle of mapping • relationship between two things; in this case, between the controls and results • natural mapping takes advantage of physical analogies and cultural standards (e.g., sound volume control) • artificial mapping schemes may be necessary when no obvious natural mapping scheme exists (e.g., gas range) • The principle of feedback • let users know condition of task in progress or whether it has been successfully completed • good feedback reduces user frustration and/or confusion

  11. Trade-offs in Knowledge Location

  12. The Psychology of Users • Falsely blaming yourself • usability testing runs into problems: no one likes to be watched because it makes them feel clumsy or stupid • If an error occurs on a task that appears simple, people tend to blame themselves -- not the design • Misconceptions of everyday life • Blaming the wrong cause • Learned and taught helplessness • people experience failure at a task; assume it can’t be done • with poor design, it’s as if we teach people to be helpless

  13. Errors Users Make • Slips -- typically occurring when we are distracted, tired, or stressed • capture errors (driving a familiar route rather than correct route) • description errors (throwing dirty clothes in garbage, not hamper) • mode errors (digital watch in wrong mode for action) • data-driven errors (dialing phone number of room I’m in) • loss-of-activation errors (forgetting why I went to kitchen) • Selective attention and the problem of focus

  14. Errors… (continued) • Errors in different task structures • wide and deep structures (chess) • shallow structures (choosing ice cream flavor) • narrow structures (cookbook) • Social pressures and errors in judgment • example of KAL 007 shot down over Soviet air space • better design can sometimes (but not always!) help reduce this type of error • forcing functions may also be effective solutions

  15. Execution and Evaluation • The “Action Cycle” explained • begin with goals: what we want to see happen • execution: what we do to the world • evaluation: comparing what happened to what we wanted • back to goals step; should they be revised? • The gulf of execution -- the difference between intentions and allowable actions. • The gulf of evaluation -- the amount of effort needed to determine how well results meet expectations.

  16. Principles of User-Centered Design • Use both knowledge in world and in head • Simplify task structures • Narrow gulfs of execution & evaluation • Get mappings right • Exploit the power of constraints • Design for error • When all else fails, standardize

  17. Why Designers Go Astray • Ignorance • Put aesthetics first • Worship complexity • Designers forget they are not typical users • Identify the wrong group of users • Designers give way to “creeping featurism”

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