Design Principles Flashcards
Accessibility
Accessibility is defined as the extent to which an individual perceives that any particular source is available for use. (Zimmer et al. 2007)
Access to physical spaces for people with disabilities has long been an important legal and ethical requirement and this is now becoming increasingly so for information spaces and interactive information systems.
Why people are excluded from Interactive IS
Physically
people can be excluded because of inappropriate siting of equipment or through input and output devices making excessive demands on their abilities.
Conceptually
people may be excluded because they cannot understand complicated instructions or obscure commands or they cannot form a clear mental model of the system.
Economically
people are excluded if they cannot afford some essential technology.
Cultural exclusion
results from designers making inappropriate assumptions about how people work and organize their lives.
Social exclusion
can occur if equipment is unavailable at an appropriate time and place or if people are not members of a particular social group and cannot understand particular social mores or messages.
Inclusive Design
Inclusive design is a more pragmatic approach that argues that there will often be reasons (e.g. technical or financial) why total inclusion is unattainable.
We all suffer from disabilities from time to time (e.g., a broken arm) that affect our abilities to use interactive information systems.
As a way of ensuring an accessible system, designers should:
■ include people with special needs in requirements analysis and testing of existing systems;
■ consider whether new features affect users with special needs (positively or negatively) and note this in the specification;
■ take account of guidelines – include evaluation against guidelines;
■ include special needs users in usability testing and beta tests.
Inclusivity analysis
■ Ensures that inadvertent exclusion will be minimized
■ Enables the identification of common characteristics that cause exclusion and which are
relatively cheap to fix.
Stability (fixed vs changing)
Incidence (common vs rare)
Solution (cheap/easy vs expensive/difficult)
Usability
Usability is defined as the extent to which a system, product or service can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use. (ISO, 2018)
A system with a high degree of usability will have the following characteristics:
■ Efficient in that people will be able to do things using an appropriate amount of effort.
■ Effective in that it contains the appropriate functions and information content, organized in an appropriate manner.
■ Easy to learn how to do things and remember how to do them after a while.
■ Safe to operate in the variety of contexts in which it will be used.
■ High utility in that it does the things that people want to get done.
System Usability Scale
The System Usability Scale (SUS) provides a “quick and dirty”, reliable tool for measuring the usability.
■ Originally created by John Brooke in 1986
■ Allows to evaluate a wide variety of products and services (incl. hardware, software, mobile devices, websites, applications)
■ Consists of 10 item questionnaire with five response options for respondents (5-Point-Likert scale ranging from “strongly agree” to “strongly disagree”)
Calculating and interpretation:
Each item’s score ranges from 0 to 4.
■ For items 1, 3, 5, 7, and 9 (the positively worded items) the score contribution is the scale position minus 1.
■ For items 2, 4, 6, 8, and 10 (the negatively worded items), the contribution is 5 minus the scale position.
■ You then multiply the sum of the scores by 2.5 to obtain the overall value of SUS.
Though the scores are 0-100, these are not percentages and should be considered only in terms of their percentile ranking.
Based on research, a SUS score above a 68 would be considered above average and anything below 68 is below average, however the best way to interpret your results involves “normalizing” the scores to produce a percentile ranking.
summary:
* SUS is reliable. Users respond consistently to the scale items, and SUS has been shown to detect differences at smaller sample sizes than other questionnaires.
* SUS is valid. That is, it measures what it purports to measure. SUS is not diagnostic. That is, it does not tell you what makes a system usable or not.
* SUS scores are not percentages, despite returning a value between0 and 100. To understand how your product compares to others, you need to look at its percentile ranking.
* SUS measures both learnability and usability.
* SUS scores have a modest correlation with task performance, but it is not surprising that people’s subjective assessments may not be consistent with whether or not they were successful using a system. Subjective assessments of usability are only one component of the overall construct of usability.
Acceptability
Acceptability is about fitting technologies into people’s lives and defines the quality of something to be accepted. (Oxford Dictionary)
An essential difference between usability and acceptability is that acceptability can only be understood in the context of use.
Key Features of Acceptability
Political.
Is the design politically acceptable? Do people trust it?
Convenience.
Designs that are awkward or that force people to do things may prove unacceptable. Designs should fit effortlessly into the situation.
Cultural and social habits.
If political acceptability is concerned with power structures and principles, cultural and social habits are concerned with the way people like to live.
Usefulness.
This goes beyond the notions of efficiency and effectiveness and concerns usefulness in context.
Economic.
There are many economic issues that render some technology acceptable or not. Price is the obvious one and whether the technology offers value for money.
Principles of Universal Design
Equitable Use: The design does not disadvantage or stigmatize any group of users.
Flexibility in Use: The design accommodates a wide range of individual preferences and abilities.
Simple, Intuitive Use: Use of the design is easy to understand, regardless of the user’s experience, knowledge, language skills, or current concentration level.
Perceptible Information: The design communicates necessary information effectively to the user, regardless of ambient conditions or the user’s sensory abilities.
Tolerance for Error: The design minimizes hazards and the adverse consequences of accidental or unintended actions.
Low Physical Effort: The design can be used efficiently and comfortably, and with a minimum of fatigue.
Size and Space for Approach and Use: Appropriate size and space are provided for approach, reach, manipulation, and use, regardless of the user’s body size, posture, or mobility.
Visual Interface Design
Interface Design is about creating an experience that enables people to make the best use of the system being designed. (Benyon 2014)
Graphical User Interface (GUI) - WIMP
WIMP - windows, icons, menus and pointers
Window is a means of sharing a device‘s graphical display resources among multiple applications at the same time.
Icon is an image or a symbol used to represent a file, folder, application or device (metaphor, direct mapping, convention).
Menu is a list of commands or options from which one can choose.
Pointing device of which the mouse is most widespread, but fingers are also used as is the stylus.
Guidelines from perception
Use proximity to organize buttons
Use continuity to connect disconnected elements
Use similarity to organize files
Use closure as closed objects are easier to perceive than those are open.
Guidelines with colors
Rule1:
Use a maximum of five, plus or minus two, colors.
Rule2: Use foveal (center) and peripheral colors appropriately.
Rule3:
Use colors that exhibit a minimum shift in color/size if the colors change in size in the imagery.
Rule4:
Do not use high-chroma, spectrally extreme colors simultaneously.
Rule5:
Use familiar, consistent color codings with appropriate references.
Rule6:
Use the same color for grouping related elements.
Rule7:
Use the same color code for applications, training, testing, and publications.
Rule8:
Use high value, high saturation colors to draw attention.
Rule9:
If possible, use redundant coding of shape as well as color.
Rule10:
Use color to enhance black-and-white information.
Guidelines for Error Message Design
- Take care with the wording and presentation of alerts and error messages
- Avoid using threatening or alarming language in messages (e.g., fatal error)
- Do not use double negatives as they can be ambiguous
- Use specific, constructive words in error messages (e.g., use ‘please enter your name’ rather than ‘invalid entry’)
- Make the system ‘take the blame’ for errors
- DO NOT USE ALL UPPERCASE LETTERS as it looks as if you are shouting Use attention-grabbing techniques cautiously (e.g., avoid over-using ‘blinks’)
- Do not use more than four different font sizes per screen
- Do not over-use audio or video
- Use colors appropriately and make use of expectations (e.g., red = danger)
Navigation Design
- Labelling
■ Labels are used for internal and external links, headings, titles, etc.
■ Iconic labels can be very useful if context and design are clear
■ Clear and unambiguous preferred vocabulary is necessary - Navigation Support
■ Global navigation bar = across the top of a site that points to the main, top-level categories
■ Local navigation bar = for sub-categories (on the left-hand side or as drop down menu)
■ “You-are-here” sign = important feature to support navigation (e.g., using breadcrumbs, highlighting current page) - Searching Mechanisms
Two main problems with searching (e.g. on a website)
■ Knowing exactly what sort of documents the search engine is searching
■ How to express combinations of search criteria: Search engines are based on Boolean logic (searching for information on “cats and dogs”)
Many aspects of physical world are relatively static, the world of information content is not. Thus, navigation is central to the development of any information space.
Visual Perception
Visual Perception is concerned with extracting meaning (and hence recognition and understanding) from the light falling on our eyes. Vision is concerned with such things as detecting color, shape and the edges of objects. (Benyon 2014)
