Usability Engineering

Manoj Chawla

Agenda• What Is Usability?• Generations of User Interfaces• The Usability Engineering Lifecycle• Usability Heuristics• Usability Testing• Usability Assessment Methods beyond Testing• Interface Standards• International User Interfaces• Future Developments

Definition• Learnability

– Easy to learn• Efficiency of Use

– Expert users steady level of performance

• Memorability– Easy to remember

• Few and No catastrophic Errors– Minimise frequency of errors

• Subjective Satisfaction– How pleasant it s to use the

system

• Issues– Users task– Users individual

characteristics– User differences

• Age, gender, reasoning ability

– Experience with the system– Experience with computers

in general– Experience with the task

domain

Usability rules• Your best guess is not good enough• The user is always right• Users are not designers• Designers are not users• Vice presidents are not users• Less is more• Details matter• Help doesn’t always help• Usability engineering is a process

Scenarios

Source: Jakob Nielson

Generations of user interfacesGeneration Hardware Technology Users Advertising

ImageUser interface paradigm

-1945 Electro/Mechanical

Blinking lights & cards

Inventors None None

1945-1955 Vacuum tubes Typewriter Experts/pioneers Calculator Programming batch

1955-1965 Transistors Line oriented terminals

Technocrats Information processor

Command languages

1965-1980 Integrated Circuits

Full screen terminal

Specialised groups w/o knowledge

Mechanisation e.g. bank tellers

Hierarchical menus and form fill-in

1980-1995 VLSI PC Professionals/Hobbyists

Personal productivity tool

WIMP

1995-? Networked PC’s Easily portable with cellular modem

Everybody Computer as appliance

Non command based interfaces

The lifecycle

• Know the User • Individual User Characteristics • Task Analysis • Functional Analysis • The Evolution of the User • Competitive Analysis • Goal Setting • Financial Impact Analysis • Parallel Design • Participatory Design • Coordinating the Total

Interface

• Guidelines and Heuristic Evaluation

• Prototyping • Scenarios • Interface Evaluation

– Severity Ratings • Iterative Design • Capture the Design Rationale • Follow-Up Studies of Installed

Systems • Meta-Methods • Prioritising Usability Activities • Be Prepared

Heuristic evaluation• Graphic design and colour• Simple and natural dialogue• Speak the users language• Minimise the users memory load• Consistency• Feedback• Clearly market exits• Shortcuts• Good error messages• Prevent errors• Help and documentation

Discount usability engineering• User and task observation

– Simple visits to customer locations, observe and be quiet let the users work normally with out interference

• Scenarios– Scenarios are prototypes with reduced functionality and

features• Simplified thinking aloud

– Test user allowed to use the system while being asked to think aloud. This allows the observer not just what but why

Usability testing• Reliability• Validity • Test Goals and Test Plans • Test Plans • Test Budget • Pilot Tests • Getting Test Users • Novice versus Expert Users • Between-Subjects versus

Within-Subjects Testing • Choosing Experimenters • Ethical Aspects of Tests with

Human Subjects • Test Tasks

• Stages of a Test– Preparation – Introduction– Running the Test – Debriefing

• Performance Measurement • Thinking Aloud • Constructive Interaction • Retrospective Testing • Coaching Method • Usability Laboratories • Cameraless Videotaping • Portable Usability Laboratories • Usability Kiosks

Measuring subjective satisfaction

• Pleasing ________ Irritating• Complete ________ Incomplete• Cooperative ________ Uncooperative• Simple ________ Complicated• Fast to use ________ Slow to use• Safe ________ Unsafe

Methods beyond testing

• Observation • Questionnaires and Interviews • Focus Groups • Logging Actual Use • Combining Logging with Follow-Up Interviews • User Feedback • Choosing Usability Methods • Combining Usability Methods

International user interface• May or may not involve translation• Icons

– Resemblance icons e.g. envelope for mail– Reference icons e.g. depicts some object– Arbitrary icons – e.g. meaning by convention

• Guidelines– Characters – more than ASCII character set– Numbers & currency– Time and measurement units

• Resource separation– Separate the interface and the system functionality

• Multi-local interfaces– Flexibility for different users to communicate

The future• Speech input/output• Individualised interaction• Increased use of graphics• Dialogues designed by users• Increase computer knowledge• System adapts to user• Natural language• Self explanatory systems without manuals• Computer support for cooperative work

Actions

• Recognise the need for usability• Provide senior management support• Devote specific resources to usability

engineering• Integrate UE activities into various stages of

development• Make sure the user interfaces are subjected

to user testing

Usability trade-offs

• Include accelerators for experts