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 • Issues
– Easy to learn – Users task
• Efficiency of Use – Users individual
– Expert users steady level of characteristics
performance – User differences
• Memorability • Age, gender, reasoning
ability
– Easy to remember
– Experience with the system
• Few and No catastrophic Errors
– Experience with computers
– Minimise frequency of errors in general
• Subjective Satisfaction – Experience with the task
– How pleasant it s to use the domain
system

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 interfaces
Generation Hardware Technology Users Advertising User interface
Image paradigm
-1945 Electro/Mechani Blinking lights & Inventors None None
cal cards
1945-1955 Vacuum tubes Typewriter Experts/pioneers Calculator Programming
batch
1955-1965 Transistors Line oriented Technocrats Information Command
terminals processor languages
1965-1980 Integrated Full screen Specialised Mechanisation Hierarchical
Circuits terminal groups w/o e.g. bank tellers menus and form
knowledge fill-in
1980-1995 VLSI PC Professionals/Ho Personal WIMP
bbyists productivity tool
1995-? Networked PC’s Easily portable Everybody Computer as Non command
with cellular appliance based interfaces
modem

The lifecycle
• Know the User • Guidelines and Heuristic
• Individual User Characteristics Evaluation
• Prototyping
• Task Analysis
• Scenarios
• Functional Analysis
• Interface Evaluation
• The Evolution of the User – Severity Ratings
• Competitive Analysis • Iterative Design
• Goal Setting • Capture the Design Rationale
• Financial Impact Analysis • Follow-Up Studies of Installed
• Parallel Design Systems
• Meta-Methods
• Participatory Design
• Prioritising Usability Activities
• Coordinating the Total
• Be Prepared
Interface

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 • Stages of a Test
• Validity – Preparation
• Test Goals and Test Plans – Introduction
• Test Plans – Running the Test
– Debriefing
• Test Budget
• Performance Measurement
• Pilot Tests
• Thinking Aloud
• Getting Test Users
• Constructive Interaction
• Novice versus Expert Users
• Retrospective Testing
• Between-Subjects versus
Within-Subjects Testing • Coaching Method
• Choosing Experimenters • Usability Laboratories
• Ethical Aspects of Tests with • Cameraless Videotaping
Human Subjects • Portable Usability Laboratories
• Test Tasks • 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