User Characteristics & Design Principles
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Lecture # 11
Objective of this lectureDescribe a set of important UI design principlesPlace these principles within the context of
human characteristics and show how they contribute to usability
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Achieving UsabilityOur objective in designing the User Interface is
to achieve a high degree of usability for our product
User Centered Design (UCD) recommends early and ongoing iterations with users
To optimize the design process we should attain as high degree of usability as we can on our first design cycle
Usability principles can help us achieve such a high degree of usability early in the design
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Usability and Product Success
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iel S
pitz
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MS BOB Renault 4 circa 1970
Users rejected anthropomorphisms Negative transfer of training resulting in many errors
• Ignoring usability can impact the bottom line and safety
Quality of the Interaction - Usability
Efficiency Effectiveness Acceptance
Learnability Error/Safety Satisfaction
PerformanceSpeed Memorability Task completion
Usability of anapplication
UsabilityIndicators
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Effective interaction is determined by the goodness of fit between interface design and operator’s characteristics, needs, task requirements
Martijn van Welie (2001)
What is a UI Design PrincipleKnowledge gained from past design experience
and usability studies It’s a guide post pointing the way to a usable
designIt is not by itself an end or a ruleOne should try and follow it when it makes
sense, and deviate from it when needed
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UI Design Principles
Know your userLet the user control
the interactionCapitalize on what the
user already knowsMaintain consistency
at the interfaceProvide effective
feedback
Expose the interaction to the user
Minimize reliance on user memory
Minimize the impact of user error
Aesthetic mattersAlways test your
interface with users
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1) Know Your User – S/he is not you
Effective user interface is one that is compatible with and focuses on the users and their tasks. It considers:General human characteristics Characteristics the users of your application
Domain specific vocabularyComputer literacyGeneral education
Task specific characteristics of your usersTouch typistsFrequency of task performance
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Self Check-In Kiosk
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Designed for the general traveling population – What can you assume about the users of this system?
2) Let the User Control the Interaction
People want to control their environmentSoftware applications should be designed to
support the users, their task, and their interaction style
Constraining users’ action is fineControlling users’ action should be avoidedControllability can impact user satisfaction
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Ways to Increase User ControlLimit the extent to which users are forced to
perform a task in a predetermined wayMinimize the use of ModesAlways allow users to cancel outAllow users to save partial work such as forms
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3) Capitalize on what Users KnowUsing metaphors or familiar idioms (cut &
paste) at the interface will enable users to instantly understand the details of the application
Reusing knowledge will significantly enhance learning or reduce the amount of learning needed to achieve proficiency
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Using Metaphor– CD Control
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Using Metaphor - PIM
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4) Maintain ConsistencyConsistency enables users to anticipate events
and reuse learned behaviors -Positive TransferIt is achieved by reusing UI design structures
within and between applicationsComplying with standards for example
Reuse of knowledge reduces learning and enhances performance
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Consistent Menu and Tool Bars
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Consistency is not Always Good
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Usability is maximized by reusing usable elements – Duplicating bad design will result in a consistently bad designThis is a poor design for water temperature control and rinsing soapy hands
When Inconsistency is Good Inconsistent structure or design can be used to
attract user attention and prevent an automated response e.g., The delete dialog box
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5) Provide Effective Feedback
Feedback closes the action loop and “enables” the user to continue with his/her task or sequence of actions
Effective feedback is feedback that is provided to users: Immediately following the user’s actionAt an appropriate level
E.g., Action, Context, System state levelAt an appropriate place
E.g., at the locus of attention
Feedback improves performance and learning
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Effective Feedback
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6) “Expose” the Interaction to the User
Let the user see clearly the functions that are available at the interface
Exposing the interaction facilitates learning and performance
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Poor Visibility
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7) Minimize Reliance on MemoryAbility of users to recall commands, object
names, sequence of actions, etc. is limitedMake the interface visual with limited reliance
on recallAllow selection rather than relying on users to
remember a command or object nameExceeding memory limits hinders performance-
errors and speed
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Supporting Memory Limitation
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One way of supporting memory limitation is to use name recognition
Supporting Memory Limitation
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A better way of supporting memory limitation is to capitalize on both name recognition and visual recognition
Supporting Memory Limitation
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Another way of supporting memory limitation with both name recognition and visual recognition
8) Minimize the Impact of ErrorCost of errors impacts user performance
We are all afraid to err or loose our workWhen possible enable users to reverse their
actions Undo Confirm delete
Else, limit the cost of error Auto Save
But don’t over protect the userEasy recovery from errors enhances user
satisfaction and performance
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9) Aesthetics MatterConsider function first, form later
But don’t ignore form
Form or presentation often sets the moods of the user which in turns impacts users’ experience
Form or presentation facilitates: Visual scanning of a dialog box, window, page Location or detection of objects
Aesthetics enhances user satisfaction and performance
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Poor Aesthetics
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Poor alignmentInconsistent use of colorsAlso poor task flow
Use Colors carefully Use of color to convey information in the interface
should be accompanied with clear secondary cues
If red vs. green is the only way to tell which section is within bounds, about 6% of all users will have trouble telling the difference (9% Male, 2% Female)
Everyone is colorblind in low light
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10) Always Test Your InterfaceWe don’t have strong models of the human
operator/userWe can not predict (but can anticipate) how
certain design attributes will effect performance or satisfaction
We use testing to assess and refine our designs
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Lecture’s Main PointsEffective interaction design is built on
understanding how human act and the factors that impact human activity within a given context
Many of these factors have been captured by UI design principles
Adhering to these design principles will significantly enhance the usability of an interface
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