1 usability guidelines, principles & theories lecture 5 date: 16 th february

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Usability Guidelines, Principles &

TheoriesLecture 5

Date: 16th February

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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

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What is Usability ?

•Usability is NOTJust common sense

all art (and no science)

stumbled onto by accident

tacked on at the endfree

• Usability ISintuitive, 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

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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 assessmenteffectively = to a specified level of human performance” (Shackel, 1990)

•Usability affords the user easy access to the product’s functions

Usability Issues

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What is Usability?

Usability Issues

Return on investment in the range of 3:1 to 100:1

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What is Usability?

Usability Issues

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

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Poor Usability ExamplesIn 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).

Usability Issues

(1) The Economist (2001, April 14). Design Darwinism.(2) Katches, M. 1997. "State kills $99 million computer."

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Usability Issues

For a system to be usable the following must be achieved (Shackel, 1990):

Usability Issues

EffectivenessEffectiveness AttitudeAttitude LearnabilityLearnability FlexibilityFlexibility

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

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Usability Issues

Other aspects of Usability:

Ease-of-use

Friendliness

Usability Issues

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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

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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

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Ease-of-Use

•Exasperation responses•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

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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

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Ease-of-Use

•Decision-making 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

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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

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Friendliness

Usability Issues

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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

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Friendliness

Desirable qualities of a systemDesirable qualities of a system

•Adaptive•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

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Friendliness

•Comprehensible•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

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Friendliness

•Self-explanatory•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

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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

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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

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Usability

Guidelines Principles Theories

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Usability


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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

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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

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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

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Getting the user’s attention

• Intensity• Marking• Size• Choice of fonts• Inverse video• Blinking• Color• Audio

Guidelines

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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

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Usability


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Principles

• More fundamental, widely applicable, and enduring than guidelines

• Need more clarification

Principles

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Principles

•For any system or product:

•Principles of Universal DesignPrinciples of Universal Design - for any system or

product used by people

•For computer systems:

•Design principlesDesign principles - tend to be used mainly for

informing a design

•Nielsen’s usability principlesNielsen’s usability principles - used mostly as the

basis for evaluating prototypes and existing systems

•Many principles of both are overlapping

Principles

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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

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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

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Equitable use

Flexibility in use

Simple and Intuitive

Perceptible Information

Tolerance for Error

Low Physical Effort

Size and Space for approach and use

Principles

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Principles of Universal design

Equitable use

Principles

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GUIDELINESGUIDELINES• 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.

1. EQUITABLE USE

The design is useful and marketable to people with diverse abilities.

Principles

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Flexibility in Use

Principles

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2. FLEXIBILITY IN USE

The design accommodates a wide range of individual preferences and abilities. GUIDELINESGUIDELINES •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

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Simple and Intuitive

Principles

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3. 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 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

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Perceptible Information

Principles

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Principles of universal design

The design communicates necessary information effectively to the user, regardless of ambient

conditions or the user's sensory abilities.

GUIDELINESGUIDELINES •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.

4. PERCEPTIBLE INFORMATION

Principles

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Tolerance for error

Principles

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5. TOLERANCE FOR ERROR

The design minimizes hazards and the adverse consequences of

accidental or unintended actions.

GUIDELINESGUIDELINES •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

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Low physical effort

Principles

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6. LOW PHYSICAL EFFORT

The design can be used efficiently and comfortably and with a

minimum of fatigue.

GUIDELINESGUIDELINES •Allow user to maintain a neutral body position. •Use reasonable operating forces. •Minimize repetitive actions. •Minimize sustained physical effort

Principles

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Size and space for approach and use

Principles

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7. SIZE AND SPACE FOR APPOACH AND USEAppropriate size and space is provided

for approach, reach, manipulation, and use regardless of user's body size,

posture, or mobility. GUIDELINESGUIDELINES •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

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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

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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

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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

1 usability guidelines, principles & theories lecture 5 date: 16 th february

Documents

aspects of usability

friendliness usability

end free usability

poor usability examples

specified slide

use ease of use

computer system

user support