CS 5150
Software Engineering
Lecture 11
Usability 2
Administrivia
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Feasibility studies
Surveys canceled
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Anonymous feedback
Team feedback
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First Presentation Contents
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Motivation, Scope & Goals
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Whatever you’ve done...
Detailed requirements, mock-ups, prototypes, system
architecture
Schedule & Plan
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DO NOT assume your audience read the feasibility study
Progress to date
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Quick -- no more than a few minutes
How are you doing relative to your plan in your feasibility
report?
Revised plan
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SE in the News
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Recent history of patents in America changed
dramatically in 1982
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One appeals court took over a lot of power
Crazy stat: Microsoft patents received in ...
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1980s:5; 1990s:1,116; 2000s:12,330
Fitocracy: Will every UI become a game?
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Interface Design
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Most human interaction with software now is
some kind of GUI
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Windows desktop, tablet, etc
Relatively easy to learn and discoverable
Support tight feedback loop
Hard to automate tasks
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Design for Direct Manipulation
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Visual components are “actors” that have state and can
be manipulated independently
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Conflict with usual programming language focus on
procedures
metaphors and mental models: Conceptual models,
metaphors, icons; may or may not be intuitive
“Navigation” in a conceptual space can engage spatial
reasoning
Use existing conventions whenever you can
look: Appearance idioms that convey meaning
feel: User input and feedback idioms
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Design Elements: Menus
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Pros:
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Certain categories of error are avoided
Enables context-sensitive help
Challenges:
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Easy for users to learn and use
Scrolling menus (e.g., states of USA)
Hierarchical
Associated control panels
Menus plus command line
Users prefer broad and shallow to deep menu systems
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Help System Design
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Help system design is harder than many programmers
assume
Must test with inexperienced users
Kinds of help systems:
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Manual
Context information
Tutorials
Cook books & wizards
Emergency
Must have many routes to help information
Never blame the user
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Information Presentation
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Simple is often preferable to pretty
Text
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precise, unambiguous
fast to manipulate and transmit
Graphical interface
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Can be easier to learn
colors and animation can convey
information
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Separation of Content from
Presentation
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Remember the Mantra: Design and
Evaluate
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Evaluations
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Quick, cheap iteration when you’re exploring a new
interface idea (early stage development)
Test usability with real users before launch/deployment (late
stage development)
Continue refining with user feedback after
launch/deployment (maintenance)
Categories of evaluation:
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Informal testing
Expert review
Measurement on the actual system
Empirical evaluation with users
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Measuring Usability
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Effectiveness
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Can the users complete their goals
(accurately) with the software
Efficiency
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Effectiveness per unit time/effort
Satisfaction
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Subjective evaluation of how pleasing or
easy the interface is
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Evaluation based on Measurement
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Basic concept: log events in the users' interactions
with a system
Examples from a Web system
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Clicks (when, where on screen, etc.)
Navigation (from page to page)
Keystrokes (e.g., input typed on keyboard)
Use of help system
Errors
May be used for statistical analysis or for detailed
tracking of individual user
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... Sometimes Called Metrics
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Analysis of system logs
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When was was the help system used?
What errors occurred and how often?
Which hyperlinks were followed (click through
data)?
Human feedback
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Which user interface options were used?
Complaints and praise
Bug reports
Requests made to customer service
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Evaluation with Users
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“Test the system, not the user”
Prepare, evaluate, analyze
Preparation
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Decide on goals (what activities do you want
to test?)
Write user tasks
Recruit participants
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Usability Lab
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User Observation Considerations
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Is environment realistic?
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Record
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Video, audio, I/O
actions
Standardized feedback
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Analyzing User Test Results
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Pay close attention to
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Any frustrations
Long pauses
Incomplete tasks
Resist impulse to blame users
Statistics can be useful, but most users
studies aren’t large enough to justify strong
statistical conclusions
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Evaluation Example: Eye Tracking
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Good for Complex UIs
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Refining Designs
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Critical to keep the roles of designer and
evaluator separate
Designers tend to assume their existing
designs are good enough too quickly
Evaluators do not understand the constraints
of the project as well
Negotiation is key!
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UI Design Tension: Control of
Appearance
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Does the designer control the UI down to the
pixel level?
Not practical in modern web apps
Can be important in modern mobile apps
Supporting multiple platforms well can be
expensive
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Usability and Cost
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Cost increases dramatically with degree of UI
innovation
Use a multi-tier user testing strategy
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office mate, expert review, small external
testing
Testing is hard to automate
Releasing hard-to-use software can be fatal
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