The document discusses usability and its components, defining usability as a measure of how effectively, efficiently, and satisfactorily users can achieve their goals with a product. It outlines the importance of usability engineering, structured processes, and the benefits of user-centered design, highlighting the usability engineering lifecycle phases. Key components of usability include learnability, efficiency, memorability, errors, and satisfaction, emphasizing the value of usability in product development.

1. Usability Engineering
Lecture 5

2.  What is Usability?
 Quality components of Usability
 Usability Engineering
 Why usability Engineering?
 Structured Process
 why we need structured process?
 Benefit of Usability Engineering
 Usability Engineering Lifecycle
Context:

3. The ISO 9241-11: Guidance on Usability [ISO9241] defines:
 “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.“
 For instance:
• Appropriate for a purpose
• Comprehensible, usable, (learnable), …
• Ergonomic, high-performance, ...
• Reliable, robust, …
What is Usability?

4. What is Usability? (Cont…)
“Usability is a quality attribute that assesses how easy user
interfaces are to use.
The word "usability" also refers to methods for improving
ease-of-use during the design process.”

5. Usability has five quality components:
 Learnability
 Efficiency
 Memorability
 Errors
 Satisfaction
Quality components of Usability :

6.  Learnability:
How easy is it for users to accomplish basic tasks the first time they
encounter the design?
 Efficiency:
Once users have learned the design, how quickly can they perform tasks?
 Memorability:
When users return to the design after a period of not using it, how easily
can they reestablish proficiency?
Quality components of Usability: (Cont…)

7.  Errors:
How many errors do users make, how severe are these errors, and how
easily can they recover from the errors?
 Satisfaction:
How pleasant is it to use the design?
Quality components of Usability : (Cont…)

8.  Usability Engineering is a discipline that provides
structured methods for achieving usability in user
interface design during product development.”
 User Interface Design describes any kind of interface design
of an interactive system and also the information design of
non-interactive systems (e.g. subway map). Thus User
Interface Design is a subset of Usability Engineering.
Usability Engineering?

9.  Computers, software and interactive systems as a
whole are simple to use and to learn.[1]
 Software is becoming more complex. every new
version of a software product has even more complex
features.
 Software is becoming more interactive.[2]
 users are often not very experienced in using
computers.
Why usability Engineering?

10.  Formally defined, standardized processes that
involve day-to-day operations , exceptions rare
and not well tolerated, process structure
changes slowly
Structured Process:

11. Five Reasons:
1. People believe they understand the behavior of others based on their
own experience
2. This belief is only lost through prediction and measurement
3. Experience changes one’s perception of the world
4. Designers of system find it easy to use, naturally
5. Often intuitions are wrong
why we need structured process?

12.  Every $1 invested in user centered design returns between $2 and $100
[Press92]
 Enhanced reliability and efficiency of the system
 Users will
o Experience satisfaction instead of frustration
o Achieve goals more effectively and efficiently
o Not waste time and energy
o Easily learn to handle the system
Benefit of Usability Engineering:

13.  Providers/producers/developers will benefit from
 Reduced financial costs
 Efficient design that adds value, not frills
 Fewer revisions
 Reduction of support costs
 Increased productivity
 Increased accessibility to maximize the potential audience
 Increase in use
 Happy and loyal customers
 Reduced development times
 Avoidance of unnecessary features
Benefit of Usability Engineering: (Cost…)

14. Similar to the software engineering lifecycle, the Usability Engineering Life Cycle
have the following phases
 Requirements Analysis:
 Who is the end user, who will use the product? User profiles are conceived.
 The Task analysis reveals task requirements and the current workflow as well
as specific conditions of use.
 Platform capabilities and constraints are recognized at this phase.
 Conceptual Model Design:
It includes reengineering the workflow and writing down the application
structure.
Usability Engineering Lifecycle:

15.  Testing and Debugging in Human Computer Interaction
means designing rapid prototypes and users test them.
 Implementation of the "final" system, delivery and
installation.
 Evaluation and refinement of the requirements lead to an
update of the product, repeating the usability engineering
life cycle.
Usability Engineering Lifecycle: (Cont…)

16. Figure : Usability Engineering Lifecycle