Técnicas de Calidad
en el Software
Sesión # 10
Good quality software
• Maintainability
• Flexibility
• Modularity
• Portability
• Reusability
• Interoperability
Operations
•
•
•
•
Accuracy
Confiability
Integrity
Usability
(Pressman, 1993)
Good quality software
• Maintainability
• Flexibility
• Modularity
• Portability
• Reusability
• Interoperability
Operations
•
•
•
•
Accuracy
Confiability
Integrity
Usability
(Pressman, 1993)
Introduction to Usability
Usability:
the extent to which a system is
easy to use by its target users.
the quality of a user’s experience
while interacting with a system.
the elegance and clarity with
which the interaction with a
system is designed.
Introduction to Usability
Usability evaluation:
A systematic procedure to assess
the extent to which a system is
being accepted and valued by its
target users.
A means for measuring how well
people can use a human-made
object or system.
Usability Testing Strategies
Expert reviews (without users)
Cognitive walkthroughs
Structured observations
Heuristic evaluations
Guidelines review
Acceptance tests (with real users)
Think aloud
Experimental studies
Survey
Usability Testing Strategies
Cognitive Walkthroughs
Involves expert evaluators and no users.
Evaluators analyze and document the steps
required for users to carry out key tasks, using a
system.
Evaluators report results and suggestions to
design team and developers.
Usability Testing Strategies
Preparing a Cognitive Walkthrough
Hire an expert evaluator (usability specialist).
Define user(s) profile(s).
Provide access to a system prototype.
Provide a list of key tasks supported by the
system.
Usability Testing Strategies
Preparing a Cognitive Walkthrough
Example: Preparing a cognitive walkthrough for Testudo
Access: www.testudo.umd.edu
Users: (a) Undergrad Students, (b) Grad Students, (c)
Student Service Officers, (d) Bursar office employees.
Key tasks: (a) login, (b) logout, (c) consult student account,
(d) consult student schedule, (e) consult student transcript.
Usability Testing Strategies
Structured Observations
Involves expert evaluators and no users.
Evaluators analyze and document particular
characteristics of a system.
Evaluators report results and suggestions to
design team and developers.
Usability Testing Strategies
Preparing a Structured Observation
Hire an expert evaluator (usability specialist).
Define user(s) profile(s).
Provide access to a system prototype.
A list of key system characteristics will be
provided by the evaluator.
Usability Testing Strategies
Preparing a Structured Observation
Example: Preparing a structured observation for Testudo
Access: www.testudo.umd.edu
Users: (a) Undergrad Students, (b) Grad Students, (c)
Student Service Officers, (d) Bursar office employees.
System characteristics: (a) Information Architecture, (b)
Icon Design, (c) Consistency, (d) Security, (e)
Interoperability, (d) Graphic Design, (e) Navigation Model.
Usability Testing Strategies
Heuristic Evaluation
Involves expert evaluators and no users.
Evaluators analyze particular
characteristics of a system to determine
conformance with pre-defined design
principles.
Evaluators report results and suggestions
to design team and developers.
Usability Testing Strategies
Heuristic Evaluation
Example of pre-defined design principles:
1.
2.
3.
4.
5.
6.
7.
8.
Strive for consistency
Cater to universal usability
Offer informative feedback
Design dialogues to yield closure
Prevent errors
Permit easy reversal of actions
Support internal locus of control
Reduce short-term memory load
(Shneiderman & Plaisant, 2005)
Usability Testing Strategies
Guidelines Review
Involves expert evaluators and no users.
Evaluators analyze particular
characteristics of a system to determine
conformance with pre-defined design
guidelines.
Evaluators report results and suggestions
to design team and developers.
Usability Testing Strategies
Guidelines review
Example of Web design guidelines for
McKeldin Library staff.
Web authoring guidelines
Web best practices
Web color palette
http://www.lib.umd.edu/itd/web/bestpr
actices/colors.html
Usability Testing Strategies
Guidelines review
Example of guidelines for the design and
development of digital collections at UMD.
Text collections
Image collections
Video collections
Audio collections
(See PDF file)
Usability Testing Strategies
Integrating results from
expert reviews
Organize regular meetings with the evaluator.
Identify those design suggestions which are
relevant and feasible.
Include design suggestions in the system
prototype.
Test the new prototype version with real users.
Usability Testing Strategies
Think Aloud
Involves real users.
Users are asked to carry out key tasks,
using a system.
A usability specialist observes and
documents users’ reactions to the system.
Evaluators report results and suggestions
to design team and developers.
Usability Testing Strategies
Preparing a Think Aloud session
Design a list of key tasks to be carried out by
users.
Invite as many representative users as possible.
Explain users that the session is about assessing
the system usability, not his/her performance.
Hire a usability specialist to run the sessions, and
to observe and document the users’ reactions
to the system.
Usability specialists will report results and
suggestions to design team and developers.
Usability Testing Strategies
Experimental Studies
Involve:
real users
objective and measurable
criteria
one or more system interfaces
statistical procedures
diverse data sources:
log analysis
eye-tracking analysis
Usability Testing Strategies
Usability measures in
experimental studies:
Time to learn
Speed of performance
Rate of errors by users
Retention over time
Subjective satisfaction
(Shneiderman & Plaisant, 2005)
Usability Testing Strategies
Survey
It is a generally acceptable
companion to expert reviews
and experimental studies.
QUIS: standard survey
instrument for usability
assessment.
Usability Testing Strategies
QUIS: Questionnaire for User Interaction
Satisfaction (www.lap.umd.edu)
1. System experience
2. Past experience
3. Overall reactions to the system
4. Screen layout
5. Terminology
6. Learning
7. System capabilities
8. Online help
9. Online tutorials
10. Media, I/O
11. Teleconferencing
12. Installation
Usability Testing Strategies
QUIS: Questionnaire for User Interaction
Satisfaction (www.lap.umd.edu)
•
Pre-defined sections
•
Pre-defined answers
•
Self-perceived user satisfaction
Issues:
•
Digital or print format?
•
Response rate
Usability Testing Plan
A usability testing plan:
Includes diverse strategies, with
users and expert reviews.
Should be part of a system design
and development project.
Depends on the nature of the
system being developed, and the
target users.