• Usability is the measure of the quality of a user’s experience when interacting with a product or system

or:

• Usability is a quality attribute that assesses how easy user interfaces are to use

1. Fit for use
2. Ease of Learning
3. Efficiency of use
4. Memorability
5. Error frequency and severity
6. Subject satisfaction

System functions as expected

• Do you expect to have to read a manual or the help?
• How much time are people prepared to invest in learning the system?
• What are peoples usability expectations for the system?

• How frequently do people make errors?
• What is the cost of the errors?

Slip:

• User understands system and goal
• Know what action they want to take
• Performs incorrect action

Mistake:

• May not even have the right goal

Better interface design.

Make the system easier to understand.

If users like the interface:

• They will make less errors.
• They will persist longer when they are having problems.

Aesthetics! How nice it looks is incredibly important in this respect.

1. Heuristic evaluation
2. Performance measurement
3. Usability studies

Usability experts using a predetermined set of criteria designed to measure the usability of a proposed design.

evaluator follows a scenario through the design and tests each step against the heuristic criteria.

evaluator makes recommendations to the design team either through a written document or during a team meeting.

Heuristic evaluation has only a 50% hit rate.

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1. Visibility of System Status
2. Match between System and the Real World
3. User Control and Freedom
4. Consistency and Standards
5. Error Prevention
6. Recognition Rather Than Recall
7. Flexibility and Efficiency of Use
8. Aesthetic and Minimalist Design
9. Help Users to Recognise, Diagnose, and Recover from Errors
10. Help and Documentation

The time it takes for a person to make a decision as a result of the possible choices.

Time to target depends on size and distance.

User test:

• Get real users to try to perform specified tasks
• Observe and record
• Ask their opinion
• Analyse results

Early and often.

The earlier those problems are found and fixed, the less expensive the fixes are.

Plan EVERYTHING!

• Use a template
• Fill in everything, even parts that are ocmpletely obvious

• Be specific!
• Record completion paths
• Step through tasks yourself

• Easiest way to gather satisfaction data
• There are several standard questionnaires

Yes! It should be scripted exactly.

• Greeting
• Ethics
• Task instructions
• Questionnaire

• Try the whole usability test out on one or two people
• After pilot fix obvious problems
• Repeat

Treat participants with respect

• Assume they are not idiots, it is the software that is wrong

Treat developers with respect

• They may have put their heart and soul into the product and worked overtime to get if finished for you to pull it apart

Make sure your report is

• Fair and accurate
• Tidy
• Free from grammar and spelling errors

1. Goal: we begin with some idea of what we want to happen; this is our goal.
2. Execution: we must then execute an action in the world.
3. World: to execute an action we must manipulate objects in the world.
4. Evaluation: we must validate our action and compare the results with our goal

1. Goal
2. Form intention \
3. Specify action   |>Execution
4. Execute Action /
5. Perceive world state     \
6. Interpret perception      |>Evaluation
7. Evaluate Interpretation /

• No!

Goal > Intention > Actions > Execution

• Perceive new state
• Interpret what we perceive
• Evaluate new state with goal

The EEC can be initiated at any point

Some goals are data-driven - initiated when an environmental event is perceived

Others are goal-driven - initiated when the person conceives of a new goal

The gap between a user's goalfor action and the means to execute that goal.

The difficulty a user has in mapping the visuals and messages from the system back into his own mental model.

cognitive representation of something that defines a logical and believable estimation as to how a thing is constructed or how it functions.

• Unscientific
• Partial
• Unstable
• Inconsistant
• Personal

Designs that align with a user’s mental model will be easier for him or her to use.

The concept of mapping describes how we make connections between things

Proper mapping can increase the usability of an interface.

Use natural mapping whenever possible.

The distance between what people want to do and the meaning of an interface element.

The distance between the physical appearance of an interface element and what it actually means.

A quality of an object, or an environment, which allows an individual to perform an action.

(Norman considers an affordance to be a relationship between an object and a user, not a property of an object)

When certain aspects of an object do not work in a way in which we assume they should.

• What may be an affordance to one person may not be to another
• The perception of affordance fosters usability
• The affordances a user may need must be present
• Affordances must not contradict the user’sexpectations

• Brainstorming
• Card sort
• Semantic networks
• Personas
• Scenarios
• Flowcharts
• Cognitive walkthroughs
• Use cases

• Structuring the information space
• Creating alternative solutions
• Determining which design concept to pursue

• discover user-centered groupings
• organize the information collected in the discovery phase
• define groupings for menus, controls and Web page content
• generate labels for menus, buttons and navigation links.

• They are quick and easy to perform.
• They can be done before any preliminary designs have been made.
• They will let you know how people organize information.
• They will expose underlying structures.

• They only involve the elements that you have written on the cards.
• They suggest solutions that imply structures.
• They become difficult to navigate with more categories.

A semantic network is a web of concepts that are linked through association.

• They allow an easy way to explore the problem space.
• They provide a way to create clusters of related elements.
• They provide a graphical view of the problem space.
• They resonate with the ways in which people process information.

• They require knowledge of the problem space.
• They can lead beyond the problem space.
• There is no formal semantics for defining symbol meaning.

Personas are archetypes of actual users, defined by the user’s goals and attributes.

A persona is created by identifying the primary stakeholders and creating an identity based on the stakeholder profiles and other collection activities such as interviews and surveys.

• A name
• Goals and motivating forces
• Behaviours and a personality

• They are quick and easy to create.
• They provide a consistent model for all team members.
• They are easy to use with other design methods.
• They make the user real in the mind of the designer.

• They can be difficult to create if the target audience is international.
• Having too many personas will make the work difficult.
• There is a risk of incorporating unsupported designer assumption.

• The basic goal
• The conditions that exist at the beginning of the task
• The activities in which the persona will engage
• The outcomes of those activities

• Simple network diagrams that identify the pages of a Web site and the navigational links between them

Or even

• Sophisticated diagrams that capture conditional junctures and computational processes

The evaluator takes the part of the primary stakeholder and tries to accomplish that stakeholder’s various tasks

• What it will look like
• What components it will require
• How the screens will be laid out

• Low-fidelity prototypes
• Evaluations
• Wireframes
• Functional prototypes

• Horizontal
• Vertical

• A horizontal prototype covers the breadth of functionality
• A vertical prototype covers the depth of functionality

• Easy an inexpensive to make
• Flexible enough to be constantly changes and rearranged
• Complete enough to yield useful feedback about specific design options

• People are more comfortable criticizing paper prototypes
• They can be used early and often.
• They are inexpensive and easy to create.
• They make design ideas visual.
• No special knowledge is required; all team members can create them.

• They are not interactive.
• They cannot be used to calculate response timings.
• They do not deal with interface issues such as color or font size

Design Effort/Effect vs. Time

• ability to impact cost and functional capabilities
• cost of design changes
• traditional design process
• Integrated Project Delivery Process

IPD basically has its bump earlier

• Use multiple independent evaluators
• Use observer to record evaluator
• Go through interface several times
• Compare interaction against list of heuristics
• Use heuristics specific to design
• List heuristic problems and how the heuristic is violated

1. Strive for consistency
2. Enable frequent users to use shortcuts
3. Offer informative feedback
4. Design dialogs to yield closure
5. Offer error prevention and simple error handling
6. Permit easy reversal of actions
7. Support internal locus of control
8. Reduce short-term memory load

1. Use both knowledge in the world and knowledge in the head.
2. Simplify the structure of tasks.
3. Make things visible: bridge the gulfs of Execution and Evaluation.
4. Get the mappings right.
5. Exploit the power of constraints, both natural and artificial.
6. Design for error.
7. When all else fails, standardize.

• Basic page layout
• Screen components

• from flowcharts and paper prototypes
• basically more evolved paper prototypes that include detailed information about the interface elements

to create template layouts that can be used to impose a consistent structure throughout the interface.

• Use layouts that are common to the domain
• Use flexible design for Web pages

Increases efficiency and promotes learning

• interactive prototypes that represent various degrees of functionality.
• can either be horizontal or vertical

• User interface independance
• Methodology and Notation
• Rapid prototyping
• Software support

• They separate interface design from internals.
• They enable multiple user interface strategies.
• They enable multiple-platform support.
• They establish the role of the user interface architect.
• They enforce standards

• They facilitate the development of design procedures.
• They help in finding ways to talk about design.
• They create project management.

• They make it possible to try out ideas very early.
• They make it possible to test, revise, test, revise, . . .
• They engage end users—managers and customers

• They increase productivity.
• They offer constraint and consistency checks.
• They facilitate team approaches.
• They ease maintenance.

• Guide interaction designers and help them make decisions that are based on established criteria
• They do not prescribe specific outcomes; they function within the context of a particular design project.

Efficiency principles.

• Presentation filter
• Comprehensibility Barrier
• Efficiency/usability
• Learnability barrier

Usability Goals

• There are two main usability goals in the framework; comprehensibility and learnability.

Design Principle Categories

• The framework also divides the design principles into twomain groups; efficiency principles and effectiveness principles.

Format to Describe Design Principles

• The framework uses the format “serves the principle of … which promotes …” to describe the different principles.
• Familiarity serves the principle of memorability, whichpromotes usability.

If the presentation is comprehensible, the comprehensibility barrier will be superseded.

This depends on the degree of efficiency/usability in the interface design.

If the user can learn the interface s/he can take advantage of the functionality and the interface will, therefore, be useful.

• An interface design that is easy to comprehend will be efficient and effective.
• If a user does not understand the interface it will be useless.

it is is based on comprehensibility: if you can’t understand it, you can’t learn it.

An interface with high usability will be easier to learn

recursive: we start with comprehensibility which affects learnability, which will in turn increase comprehensibility