8 HCI Usability Engineering

Embed Size (px)

Citation preview

  • 8/10/2019 8 HCI Usability Engineering

    1/34

    CISB213 Human Computer Interaction

    Usability Engineering

    1

  • 8/10/2019 8 HCI Usability Engineering

    2/34

    Learning Outcomes

    At the end of this lecture, you should be able to:

    Define the term UsabilityEngineering

    Describe the various steps involved in UsabilityEngineering Lifecycle

    Apply Usability Engineering Lifecycle in designing any

    system or application

  • 8/10/2019 8 HCI Usability Engineering

    3/34

    Key Terms you must be able to use

    Ifyou have mastered this topic, you should be able to use

    the following terms correctly in your assignments and

    exams:

    Usability engineering Usability lifecycle

    Usability goals

  • 8/10/2019 8 HCI Usability Engineering

    4/34

    Usability

    Usability: the extent to which a product can be used by

    specified users to achieve specified goals with effectiveness,

    efficiency and satisfaction in a specified context of use.

  • 8/10/2019 8 HCI Usability Engineering

    5/34

    Usability

    Why is usability important?

    It makes the difference between performing a taskaccurately and completely or not, and enjoying theprocess or being frustrated.

    Determine the success or failure of a system

    Poor usability

    Reduce productivity

    Increase cost time and effort

  • 8/10/2019 8 HCI Usability Engineering

    6/34

    Usability usually refers to software but is relevant

    to any product. Some ways to improve usability

    include: shortening the time to accomplish tasks,

    reducing the number of mistakes made,

    reducing learning time,

    and improving people's satisfaction with a system.

    Usability

  • 8/10/2019 8 HCI Usability Engineering

    7/34

    According to Jakob Nielsen (2003), usability is defined by 5

    quality components :

    Learnability : ease of learning for novice users.

    Efficiency : steady-state performance of expert users.

    Memorability : ease of using system intermittently for casualusers.

    Errors : error rate for minor and catastrophic errors.

    Subjective Satisfaction : how pleasant the system is to use.

    Usability

  • 8/10/2019 8 HCI Usability Engineering

    8/34

    Learning Curves

    Some systems are designed to focus on learnability.

    Others emphasise efficiency for proficient users.

    Some support a combination of ease of learning and anexpertmode(for example rich menus and dialogues plus acommand/ scripting language)

  • 8/10/2019 8 HCI Usability Engineering

    9/34

    Domain & Expertise

    ExtensiveComputer

    Experience

    Ignorant

    A

    boutthe

    Domain

    MinimalComputer

    Experience

    K

    nowledg

    e

    ableAbou

    t

    t

    heDomain

  • 8/10/2019 8 HCI Usability Engineering

    10/34

    Relationship between Usability Goals and User Types

    Novice Users:No or limited knowledge of the occupational task tobe performed, and of computers and interfaceconcepts or

    Knowledge of the occupational task to be performed,andof computers and interface concepts

  • 8/10/2019 8 HCI Usability Engineering

    11/34

    Relationship between Usability Goals and User Types

    Knowledgeable Intermittent Users:Understanding of the task concepts

    Broad knowledge of computers and interface

    concepts.Intermittently use the system and may therefore haveproblems with retention

    Expert Frequent (Power) Users:Thoroughly familiar with both task and interfaceconcepts. They are likely to use the system often andappreciate short cuts to speed their work.

  • 8/10/2019 8 HCI Usability Engineering

    12/34

    Typical Ways of Measuring Usability

    Learnability: pick novice users of system, measure time to

    perform certain tasks.

    Distinguish between the various timings taken for some general

    computer experience.

  • 8/10/2019 8 HCI Usability Engineering

    13/34

    Typical Ways of Measuring Usability

    Efficiency : decide definition of expertise, get sample expert

    users (which tends to be difficult), measure time taken to

    perform typical tasks.

  • 8/10/2019 8 HCI Usability Engineering

    14/34

    Typical Ways of Measuring Usability

    Memorability : get sample casual users (who are usually away

    from system for certain time/duration) and measure time to

    perform typical tasks.

  • 8/10/2019 8 HCI Usability Engineering

    15/34

    Typical Ways of Measuring Usability

    Errors : count minor and catastrophic errors made by users while

    performing some specified task.

  • 8/10/2019 8 HCI Usability Engineering

    16/34

    Typical Ways of Measuring Usability

    Satisfaction : ask users subjective opinion (questionnaire,

    interview), after trying system for real task.

  • 8/10/2019 8 HCI Usability Engineering

    17/34

    Usability Engineering

    The term usability engineering describes a process of userinterface development, sometimes referred to as user centreddesign.

    It is a lifecycle process that puts an early emphasis on userand task analysis and actual user involvement in the designand testing of a product.

    A product developed with such a user centred process is likely

    to be a more usable product than one that is developedindependent of user considerations and involvement.

  • 8/10/2019 8 HCI Usability Engineering

    18/34

    UsabilityEngineering Lifecycle

    Parallel Design Sketches

    Participatory Design

    Iterative Design

    Final Released Product

    Users, Tasks,

    Environment Analysis

    Usability Goals , Competitive Analysis

    First Prototype

    Formative Testing

  • 8/10/2019 8 HCI Usability Engineering

    19/34

    1. Identify user requirements and problems

    Profile Users

    Task Analysis

    2. Identify usability goals based on user requirements3. Checkout similar products

    4. Design and prototype a solution (involve users)

    5. Evaluate prototype

    Usability testing (real users and real tasks)

    6. Reiterate steps 4-5 until users are satisfied

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    20/34

    Identify user requirements and problems:

    Define your user population.

    Determine the distribution of skills, knowledge andexperience within your user population.

    Assess the users skill level with respect to both thetask and computer domain.

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    21/34

    Identify user requirements and problems:

    Typical Profile:

    40 % Novice Users

    57 % Knowledgeable/Intermittent Users

    3 % Expert Users

    Other Important Information:

    10 % of user population colour blind

    15 % are the elderly

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    22/34

    Identify user requirements and problems:

    Task analysis allows a designer to identify the goals andpurposes of the intended user group.

    This used to involve further analysis of userrequirements or investigation/observation of

    customers

    Used to guide user interface design

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    23/34

    Identify usability goals based

    Learnability, Efficiency, Memorability, Error, Subjective

    Satisfaction

    Decide in advance on usability metrics and desired level of

    measured usability

    E.g.

    Usability Engineering Lifecycle

    Errors Per Hour

    Optimal Target Current Unacceptable

    0 1 - 3 4.5 > 5

  • 8/10/2019 8 HCI Usability Engineering

    24/34

    Check out similar products (Competitive Analysis)

    Competitive analysis of software components

    Competitive analysis of competing systems

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    25/34

    Parallel Design (Explore design alternatives)

    designers should work independently, then compare draft

    designs

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    26/34

    Participatory Design

    Have access to pool of representative users.

    Guided discussion of prototypes, paper mock-ups,screen designs with representative users.

    E.g. Card Sorting

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    27/34

    Card Sorting - 1

    Card sorting is a technique for exploring how people group

    items, so that you can develop structures that maximize

    the probability of users being able to find items

    Is easy and cheap to conduct

    Enables you to understand how realpeopleare likely

    to group items

    Identifies terminology that is likely to bemisunderstood.

  • 8/10/2019 8 HCI Usability Engineering

    28/34

    Card Sorting - 1

    E.g. How would you group these tasks into 3 groups? (File, Edit,

    View)

    open, cut, normal view, close, copy, zoom in, save, paste, zoom

    out, save, select, toolbar, print

  • 8/10/2019 8 HCI Usability Engineering

    29/34

    Card sorting is also a technique for allowing users actualselections out of several options to determine final designdecisions

    Is easy and cheap to conduct Enables you to determine actual preferences versus

    what users thinkthey prefer

    Allows for more accurate understanding by user since

    actual examples are seen

    Card Sorting - 2

  • 8/10/2019 8 HCI Usability Engineering

    30/34

    Title

    Content

    Title

    Content

    Title

    Content

    Title

    Content

    Title

    Content

    Title

    Content

    Title

    Content

    Title

    Content

    A B C D

    E F G H

    Card Sorting - 2

  • 8/10/2019 8 HCI Usability Engineering

    31/34

    Applying Guidelines

    Guidelines . . . general principles and advice about

    usability characteristics of interfaces

    Can be intimidatingoften hundreds or thousands of

    specific recommendations.

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    32/34

    Prototyping & Testing

    Perform usability evaluation as early as possible in the design

    cycle by building and evaluating prototypes

    Usability Engineering Lifecycle

  • 8/10/2019 8 HCI Usability Engineering

    33/34

    Learning Outcomes revisited

    Check yourself to see if you can now:

    Define the term Usability Engineering

    Describe the various steps involved in Usability

    Engineering Lifecycle

    Apply Usability Engineering Lifecycle in designing any

    system or application

  • 8/10/2019 8 HCI Usability Engineering

    34/34

    Q & A