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CMC/CC A Usability Evaluation. Master IK, CIW, MMI L.M. Bosveld-de Smet Course 4; mon. 02/10/06; 16.00-18.00. Usability Evaluation. Design of interaction Dix et al. (2004). What is wanted. Analysis. Design. Usability Evaluation. Implement and deploy. Prototype.

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CMC/CC AUsability Evaluation

Master IK, CIW, MMI

L.M. Bosveld-de Smet

Course 4; mon. 02/10/06; 16.00-18.00


Usability Evaluation


Design of interactionDix et al. (2004)

What is

wanted

Analysis

Design

Usability

Evaluation

Implement

and deploy

Prototype


Design process of usable interactive systems

  • Interaction design process

    • Complex

    • Iterative

    • Never complete

  • User-centered design

    • Within software engineering framework

  • Design rules

  • Implementation support

  • Evaluation techniques

  • Universally accessible designs

  • Provision of user support


3 related concepts

  • Usability: measure of success of a product

  • User-Centered Design: design involving user participation

  • Usability Engineering:

    • Whole process ensuring usable interactive systems

    • Process aiming at systems fit for the user, the task, the environment

    • Process implying user participation during software development

    • Process committing itself to design-evaluate-redesign development cycle

    • In search for objective measures for user interface


Usability: different views

  • Same intuitions vs. Different approaches

  • Different views on:

    • Definition of usability

      • Usability attributes

    • Importance of user-centered design

    • When and how to deal with user participation

    • How to build usable systems

    • How to measure usability


Usability Attributes: Shackel’s view

  • “A usable product is one that users find satisfactory for the tasks for which it was designed.”

  • “Good design for usability depends upon achieving successful harmony in the dynamic interplay between user, task, system, and environment.”

  • Usability: 4 usable criteria

    • Learnability

    • Effectiveness

    • Attitude

    • Flexibility


Usability Attributes: ISO definition

  • “Usability is the effectiveness, efficiency and satisfaction with which specified users can achieve specified goals in particular environments.”

    • Effectiveness: “accuracy and completeness with which users achieve specific goals”

    • Efficiency: “accuracy and completeness of goals in relation to resources expended”

    • Satisfaction: “comfort and acceptability of the system”


An aside: User Interface Standards

  • Disadvantages:

    • Constrain design

    • Stagnate innovation

    • Describe principles, do not provide solutions

    • Become quickly obsolete

  • Advantages:

    • Define ‘good practice’

    • Affect attitudes w.r.t. ‘software development’


User-Centered Design: Karat’s view

  • Karat (1996) “UCD: Quality or Quackery?”

  • “UCD is an iterative process whose goal is the development of usable systems, achieved through involvement of potential users of a system in system design”

  • “I suggest we consider UCD a nice fluffy little catch phrase. It captures a commitment that the usability community supports – that you must involve users in system design – while leaving fairly open how this is accomplished”


UCD: a more objective view

  • UCD can be accomplished through the application of Usability Engineering

  • Design should centre on users

  • End-user should be consulted

  • Needs of end-users should be considered


HCI in software process

  • Software engineering

  • Usability engineering

  • Iterative design practices

  • Design rationale


Waterfall model

Requirements

Specification

Architectural

design

Detailed

Design

Implementation

and Unit testing

Integration and

Testing

Operation and

Maintenance


Usability Engineering

  • Usability specification as part of requirements specification

  • Iteration and testing

  • List of usability measurement requirements

    (Whiteside, Bennett and Holtzblatt, 1988)

    • Time to complete a task

    • Ratio of successes to failures

    • Time spent in errors

    • Number of commands used

    • Frequency of help and documentation use


Iteration in waterfall model

Requirements

Specification

Architectural

design

Detailed

Design

Implementation

and Unit testing

Integration and

Testing

Operation and

Maintenance


Usability Engineering LifecycleFaulkner (2000)

  • Know the user

  • Know the task

  • User requirements capture

  • Setting usability goals

  • Design process

  • Apply guidelines, heuristics

  • Prototyping

  • Evaluation with users

  • Redesign and evaluation with users

  • Evaluation with users and report


Role of prototyping

Design

OK?

Prototype

Evaluate

Done!

Not OK?

Redesign


Iterative design and prototyping

  • Three main approaches to prototyping

    • Throw-away prototyping within requirements specification

    • Incremental prototyping within the life cycle

    • Evolutionary prototyping throughout the life cycle


Throw-away prototyping

Preliminary

Requirements

Build

Prototype

Evaluate

Prototype

Adequate?

no

Final

Requirements

yes


Evolutionary prototyping

Req

Build Prototype

Arch

Det

Evaluate

Prototype

Impl

Int

Operation and

Maintenance


Usability Evaluation (UE)

  • Methodologies for measuring usability aspects of system’s user interface and identifying specific problems (Dix et al. 1998; Nielsen 1993)

  • Should occur throughout design life cycle

  • Common activities:

    • Capture

    • Analysis

    • Critic

  • There is a wide range of UE techniques

  • Each technique has its own requirements

  • Different techniques uncover different usability problems


Taxonomies of UE (1)

  • Formative vs. Summative

  • Analytical vs. Empirical

  • Expert analysis vs. User participation

    • Analytic methods

    • Review methods

    • Model-based methods

      vs.

    • Experimental methods

    • Observational methods

    • Query methods


Taxonomies of UE (2)

  • Automated vs. Non-automated

  • Ivory and Hearst (2001):

    • Testing

    • Inspection

    • Inquiry

    • Analytical modeling

    • Simulation


Expert Analysis


Controlled Experiment


User participation


Important factors choice UE

  • Stage in cycle at which UE is carried out

  • Style of UE

  • Level of subjectivity or objectivity of UE technique

  • Type of measures provided

  • Information provided

  • Immediacy of response

  • Level of interference implied

  • Resources required


Analytic UE techniques


Experimental and query UE techniques


Observational UE techniques


Monitoring UE techniques


Vocabulary application

  • Task analysis

  • Feasability study

  • Design representation


Feasibility study

  • Why is system needed?

  • How will system help to improve user task performance?

  • Are there critical processes that need to be supported by system?

  • What are the technical implications?

  • Can system be produced within given budget?

  • Is there a timescale for the development of the system?


Strategies for representing design

  • Storyboards

  • State transition diagrams

  • Simulations

  • Scenarios

  • Rapid prototyping

  • Wizard of Oz


Storyboard


State Transition Diagram


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