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

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

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

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

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

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

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. 1997. "State kills $99 million computer." Usability Issues

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

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

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

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

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

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

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

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

Friendliness Usability Issues

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

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

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

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

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

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

Usability Guidelines Principles Theories

Usability Guidelines Principles Theories

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

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

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

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

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

Usability Guidelines Principles Theories

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

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

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

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

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

Principles of Universal design Equitable use Principles

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

Principles of Universal Design Flexibility in Use Principles

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

Principles of Universal Design Simple and Intuitive Principles

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

Principles of Universal Design Perceptible Information Principles

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

Principles of Universal Design Tolerance for error Principles

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

Principles of Universal Design Low physical effort Principles

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

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

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

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

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

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