1. Usability Guidelines, Principles & Theories
Lecture 5
Date: 16th February

2. Overview of Lecture Introduce “Usability” Guidelines Principles
Principles of Universal Design
Major design principles
Nielsen’s usability principles
Theories
GOMs
7 Stages-of-Action
Levels of Analysis

3. What is Usability ? Usability is NOT Usability IS Just common sense
all art (and no science)
stumbled onto by accident
tacked on at the end
free
Usability IS
intuitive, safe, error-free, enjoyable
best designed in from the beginning
best achieved by knowing your users
“The best predictor of customer satisfaction”
“The next competitive frontier”
Usability Issues

4. What is Usability? Usability can be defined as:
“the capacity to be used by humans easily and effectively where,
easily = to a specified level of subjective assessment
effectively = to a specified level of human performance” (Shackel, 1990)
Usability affords the user easy access to the product’s functions
Usability Issues

5. What is Usability? Return on investment in the range of 3:1 to 100:1
Usability Issues

6. What is Usability? The payoffs included:
Fewer last-minute design changes
Usable, appealing, and effective designs
Simple, less costly documentation
Credible marketing claims
Compelling product demonstrations
Increased sales
Reduced need for customer support
Longer market life
Usability Issues

7. Poor Usability Examples
In a study of online merchandise purchases, “almost half of all attempts to make a purchase failed because the users could not work out how to complete the transaction.” (1)
On behalf of the state of California, Lockheed Martin Information Management Systems built a computer system that would improve the state's child support collection rate.
new child-support collection cases dropped 40% in the first six months of use
900 problems were documented, ranging from confusing software to vanishing parent records, t
$99 million system was scrapped in November 1997-> most costly failed computer project in state government history (2).
The Economist (2001, April 14). Design Darwinism.
Katches, M "State kills $99 million computer."
Usability Issues

8. Usability Issues
For a system to be usable the following must be achieved (Shackel, 1990):
Effectiveness
Attitude
Learnability
Flexibility
Tasks are:
completed better than required level of performance,
by some required percentage of users,
with-in some required proportion of the range of usage environments
Within acceptable range of human comfort – tiredness, discomfort, frustration, human effort
Satisfaction causes continued and enhanced usage of the system
Within time from commissioning and start of user training
Specified training time and user support
Specified re-learning time for intermittent
With flexibility allowing adaptation to some specified percentage variation in tasks and/or environments beyond those first specified
Usability Issues

9. Usability Issues Other aspects of Usability: Ease-of-use Friendliness

10. Ease-of-Use Ease of use - a fundamental design criterion for a system
What constitutes a system that has a high ease of use characteristic?
One of the earliest attempts to define ease of use was by Miller who proposed the following criteria to measure it
Usability Issues

11. Ease-of-Use Training time required to achieve satisfactory performance
critical that users be able to learn to operate a system within the time they allot to the learning process
Number of errors
users must show a reasonable error rate which can be measured in units of time or operations
Integration of automated and non-automated tasks
the fit must be achieved quickly and with few errors
Usability Issues

12. Ease-of-Use Exasperation responses Habit formation rate
High frequency points to possible strong rejection of system.
Habit formation rate
how quickly users automate their actions.
Number of users who want to use the system
if they don’t want to use it, that may say something about the design
Usability Issues

13. Ease-of-Use Irrelevant supporting actions required to perform a task
incidental actions required for, but not directly related to doing a job. Example: extensive log-on procedures etc.
Irrelevant display events
information that must be disregarded but that use up time and effort the user could be devoting to relevant tasks
Time and frequency for user warm-up
how long it takes the user to relearn the necessary skills involved in using infrequently used tools/options
Usability Issues

14. Ease-of-Use Decision-making time Failure recovery time
amount of time required to decide what to do after receiving all the information necessary to analyse a problem and select a suitable solution
Failure recovery time
amount of time and number of operations required for the user to recover from failures by either operator of system errors
Usability Issues

15. Friendliness
Another commonly used term that is used to refer to computer systems is ‘friendly’
What exactly is meant by a ‘friendly system’?
A system that scores high on the usability scale also scores highly on the friendliness scale
But does it mean something more?
Maybe the harmonious interaction of all the ease of use criteria?
Usability Issues

16. Friendliness
Usability Issues

17. Friendliness
A computer system should, like a friend, be pleasant to be with
Both friends and computer systems should possess desirable qualities
A number of researchers have tried to determine what these desirable qualities are
Some of their findings follow……...
Usability Issues

18. Friendliness Desirable qualities of a system Adaptive Transparent
a system must be adaptable to the physical, emotional, intellectual and mental needs of the user
Transparent
a system must permit one’s attention to be focused entirely on the task or job being performed, without concern for the mechanics of the interface or system
Available
any system unavailability will create dissatisfaction
Usability Issues

19. Friendliness Comprehensible Natural Predictable
the user should know what to look at, what to do, why to do it and how to do it.
Natural
operations should mimic the users behaviour patterns. Dialogues should mimic his thought processes and vocabulary
Predictable
system actions should be expected within the context of other actions that are performed
Usability Issues

20. Friendliness Self-explanatory Forgiving Efficient
steps to complete a process should be obvious and where not, be clarified by the system itself.
Forgiving
A system should be tolerant of the human capacity to make errors.
Efficient
Eye and hand movements must not be wasted. Attention should be directed to relevant controls and displays of information
Usability Issues

21. Primary Goals of Usability
Effective to use
Efficient to use
Safe to use
Have good utility
Easy to learn
Easy to remember how to use
Usability Issues

22. Usability Guidelines are a basis for determining a course of action
Principles are basic rules that guide or influence thoughts or actions
Theories are general principles that explain or predict facts or events

23. Usability
Guidelines
Principles
Theories

24. Usability
Guidelines
Principles
Theories

25. Guidelines Develop a shared language Promote consistency
Record best practices
4 sample guidelines (Shneiderman & Plaisant, 2005):
Navigating the interface
Organizing the display
Getting the user’s attention
Facilitating data-entry
Guidelines

26. Navigating the interface
Sample of the National Cancer Institutes guidelines:
Standardize task sequences
Ensure that embedded links are descriptive
Use unique and descriptive headings
Use check boxes for binary choices
Develop pages that will print properly
Use thumbnail images to preview larger images
Guidelines

27. Organizing the display
Smith and Mosier (1986) offer five high-level goals
Consistency of data display
Efficient information assimilation by the user
Minimal memory load on the user
Compatibility of data display with data entry
Flexibility for user control of data display
Guidelines

28. Getting the user’s attention
Intensity
Marking
Size
Choice of fonts
Inverse video
Blinking
Color
Audio
Guidelines

29. Facilitating data entry
Smith and Mosier (1986) offer five high-level objectives as part of their guidelines for data entry
Consistency of data-entry transactions
Minimal input actions by user
Minimal memory load on users
Compatibility of data entry with data display
Flexibility for user control of data entry
Guidelines

30. Usability
Guidelines
Principles
Theories

31. Principles
More fundamental, widely applicable, and enduring than guidelines
Need more clarification
Principles

32. Principles For any system or product:
Principles of Universal Design - for any system or product used by people
For computer systems:
Design principles - tend to be used mainly for informing a design
Nielsen’s usability principles - used mostly as the basis for evaluating prototypes and existing systems
Many principles of both are overlapping
Principles

33. Principles of Universal Design
Produced by a working group of architects, product designers, engineers and environmental design researchers
Defined a set of principles to guide a wide range of design disciplines included products and communications
These seven principles may be applied to evaluate existing designs, guide the design process and educate both designers and consumers about the characteristics of more usable products and environments
Principles

34. Principles of Universal Design
Beneficiaries of universal design include:
People in a noisy shopping mall who cannot hear a kiosk
People who are driving their car who must operate their radio or phone without looking at it
People who left their glasses in their room
People who are getting older
People with disabilities
Almost anyone
Principles

35. Principles of Universal Design
Equitable use
Flexibility in use
Simple and Intuitive
Perceptible Information
Tolerance for Error
Low Physical Effort
Size and Space for approach and use
Principles

36. Principles of Universal design
Equitable use
Principles

37. Principles of Universal Design
EQUITABLE USE
The design is useful and marketable to people with diverse abilities.
GUIDELINES
Provide the same means of use for all users: identical whenever possible; equivalent when not.
Avoid segregating or stigmatizing any users.
Provisions for privacy, security, and safety should be equally available to all users.
Make the design appealing to all users.
Principles

38. Principles of Universal Design
Flexibility in Use
Principles

39. Principles of Universal Design
2. FLEXIBILITY IN USE
The design accommodates a wide range of individual preferences and abilities.
GUIDELINES
Provide choice in methods of use.
Accommodate right- or left-handed access and use.
Facilitate the user's accuracy and precision.
Provide adaptability to the user's pace.
Principles

40. Principles of Universal Design
Simple and Intuitive
Principles

41. Principles of Universal Design
SIMPLE AND INTUITIVE
Use of the design is easy to understand, regardless of the user's experience, knowledge, language skills, or current concentration level.
GUIDELINES
Eliminate unnecessary complexity.
Be consistent with user expectations and intuition.
Accommodate a wide range of literacy and language skills.
Arrange information consistent with its importance.
Provide effective prompting and feedback during and after task completion
Principles

42. Principles of Universal Design
Perceptible Information
Principles

43. Principles of universal design
The design communicates necessary information effectively to the user, regardless of ambient conditions or the user's sensory abilities.
4. PERCEPTIBLE INFORMATION
GUIDELINES
Use different modes (pictorial, verbal, tactile) for redundant presentation of essential information.
Provide adequate contrast between essential information and its surroundings.
Maximize "legibility" of essential information.
Differentiate elements in ways that can be described (i.e., make it easy to give instructions or directions).
Provide compatibility with a variety of techniques or devices used by people with sensory limitations.
Principles

44. Principles of Universal Design
Tolerance for error
Principles

45. Principles of Universal Design
TOLERANCE FOR ERROR
The design minimizes hazards and the adverse consequences of accidental or unintended actions.
GUIDELINES
Arrange elements to minimize hazards and errors: most used elements, most accessible; hazardous elements eliminated, isolated, or shielded.
Provide warnings of hazards and errors.
Provide fail safe features.
Discourage unconscious action in tasks that require vigilance.
Principles

46. Principles of Universal Design
Low physical effort
Principles

47. Principles of Universal Design
6. LOW PHYSICAL EFFORT
The design can be used efficiently and comfortably and with a minimum of fatigue.
GUIDELINES
Allow user to maintain a neutral body position.
Use reasonable operating forces.
Minimize repetitive actions.
Minimize sustained physical effort
Principles

48. Principles of Universal Design
Size and space for approach and use
Principles

49. Principles of Universal Design
7. SIZE AND SPACE FOR APPOACH AND USE
Appropriate size and space is provided for approach, reach, manipulation, and use regardless of user's body size, posture, or mobility.
GUIDELINES
Provide a clear line of sight to important elements for any seated or standing user.
Make reach to all components comfortable for any seated or standing user.
Accommodate variations in hand and grip size.
Provide adequate space for the use of assistive devices or personal assistance
Principles

50. Principles of Universal Design
Particularly important for systems or products to be available to the public
Closely linked with research on disabilities
These seven principles may be applied to evaluate existing designs, guide the design process and educate both designers and consumers about the characteristics of more usable products and environments
Principles

51. Summary of Lecture
Usability can be defined as the capacity to be used by humans easily and effectively
Ease-of-use
Friendliness
Guidelines- provided a number of sample guidelines
Principles - introduced major principles in HCI
Principles of Universal Design
Major design principles
Nielsen’s usability principles
Theories
Conclusion

52. Terms of Reference Norman, D. (1990) The Design of Everyday Things
Preece, J. et al. (2002) Interaction Design
Shneiderman, B. & Plaisant, C. (2005) Designing the User Interface
Shackel, B. (1990) Human Factors and Usability
Smith, S. & Mosier, J. (2005) Guidelines for Designing User Interface Software
Foley, J. & Van Dam, A. (1995) Computer Graphics: Principles & Practices in C
Card, S. & Newell, A. (1983) The Psychology of Human- Computer Interaction
Karat, C. (1990) Cost-benefit analysis of usability engineering techniques
Miller, R. B. (1971) Human ease of use criteria and their tradeoffs
References