Course Introduction; Principles of Good Design

1
Course IntroductionPrinciples 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

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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

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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
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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

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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
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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
  cant be done
• with poor design, its 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
  Im 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.

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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