1 Usability Guidelines, Principles & Theories Lecture 4 DeSiaMore

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Usability Guidelines, Principles &

TheoriesLecture 4

DeSiaMore www.desiamore.com/ifm

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Overview of Lecture•Introduce “Usability”

•Guidelines

•Principles•Principles of Universal Design•Major design principles•Nielsen’s usability principles


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What is Usability ?•Usability is NOT

Just 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 IssuesDeSiaMore www.desiamore.com/ifm

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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 IssuesDeSiaMore www.desiamore.com/ifm

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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•$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

Other aspects of Usability:

Ease-of-use

Friendliness


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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


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Ease-of-Use•Training time required to achieve satisfactory performance•Number of errors•Integration of automated and non-automated tasks•Habit formation rate•Number of users who want to use the system•Irrelevant supporting actions required to perform a task•Irrelevant display events•Time and frequency for user warm-up•Decision-making time•Failure recovery time


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Ease-of-Use•Is Rational Rose easy to use??


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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?


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Friendliness


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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……...


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FriendlinessDesirable qualities of a systemDesirable qualities of a system•Adaptive•Transparent•Available•Comprehensible•Natural•Predictable•Self-explanatory•Forgiving•Efficient

How does Rational Rose rate?


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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


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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• Organising the display• Getting the user’s attention• Facilitating data-entry

GuidelinesDeSiaMore www.desiamore.com/ifm

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Navigating the interface• Sample of the National Cancer

Institutes guidelines:• Standardise 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


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Organising 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


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Getting the user’s attention• Intensity• Marking• Size• Choice of fonts• Inverse video• Blinking• Colour• Audio


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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


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Usability



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Principles

• More fundamental, widely applicable, and enduring than guidelines

• Need more clarification

PrinciplesDeSiaMore www.desiamore.com/ifm

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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


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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


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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



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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


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Principles of Universal design

Equitable use


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GUIDELINESGUIDELINES• Provide the same means of use for all

users: identical whenever possible; equivalent when not.

• Avoid segregating or stigmatising 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.


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Flexibility in Use


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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.


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Simple and Intuitive


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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


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Perceptible Information


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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


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Tolerance for error


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5. TOLERANCE FOR ERROR

The design minimises hazards and the adverse consequences of

accidental or unintended actions. GUIDELINESGUIDELINES

•Arrange elements to minimise 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.



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Low physical effort


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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. •Minimise repetitive actions. •Minimise sustained physical effort


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Size and space for approach and use


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Principles of Universal Design7. 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. 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


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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



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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

ConclusionDeSiaMore www.desiamore.com/ifm

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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

ReferencesDeSiaMore www.desiamore.com/ifm

Documents

1 Usability Guidelines, Principles & Theories Lecture 4 DeSiaMore