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Usability Engineering
Bettina Thurnher
Institute of Software Technology and fS f
Interactive Systems (IFS)
Vienna University of Technology

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Outline
Definition & Moti ation
Motivation
The Usability Process y Usability Methods
Usability d Process M d l
U bilit and P
Model
Mobile Usability Engineering y g g Web Usability

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Definition & Motivation

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What is usability?
 Usability: a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use Appropriate f a purpose
A
i t for
Comprehensible, usable, (learnable), …
Ergonomic, hi h
E
i high-performance, … f Reliable, robust, …

 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

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What is usability?
 Five quality components
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? Errors: How many errors do users make, how severe y , are these errors, and how easily can they recover from the errors?
Satisfaction: How pleasant is it to use the design?

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What is usability?
 A model of the attributes of system acceptability

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What is usability?
 Traditional software development vs human vs. humancentered development

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What is usability?
 Usability is a measurable characteristic of a product user interface that is present to a greater or lesser degree
 One broad dimension of usability is how easy to learn th user i t f l the interface i f novice and casual is for i d l users
 Another is how easy to use (efficient, flexible, powerful) the user interface is for frequent and proficient users, after they have mastered the initial learning of the interface

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Usability Engineering and User
Interface Design
 Usability Engineering is a discipline that provides structured methods for achieving usability in user interface design during product development
 User Interface Design is a subset of Usability
Engineering
E i i 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)

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Why Usability Engineering?
Software
Soft are
More complex
More interactive
Users are not very experienced y p

It is very important, that computers, software and interactive systems as a whole are simple to use and to learn

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Why Usability Engineering?
 Five reasons by why there is a need for a structured process to increase usability
People b li
P
l believe th understand th b h i of others they d t d the behavior f th based on their own experience
This belief is only lost through prediction and measurement Experience changes one’s perception of the world one s
Designers of system find it easy to use, naturally
Often intuitions are wrong

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The Benefit of Usability Engineering
 Every $1 invested in user centered design returns between $2 and $100
U
Users
Experience satisfaction instead of frustration
Achieve goals more effectively and efficiently
Not waste time and energy
Easily learn to handle the system

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 Providers/producers/developers
Reduced financial costs
Efficient design that adds value, not frills g Fewer revisions
Reduction of support costs
Increased productivity
Increased accessibility t maximize th potential
I
d ibilit to i i the t ti l audience Increase in use
I
i
Happy and loyal customers
Reduced development times
Avoidance of unnecessary features

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The Usability Process

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Software Engineering Lifecycle
 Most of the software engineering processes are iterative processes. This process leads to a product or an updated version of the product
Requirements Analysis, what to design and why, and what goals should b achieved d h t l h ld be hi d Development of a Concept; how to get to a product
Implementation of the Concept
Testing and Debugging g gg g
Delivery and Installation
Maintenance, i.e.
Maintenance i e evaluation of the current installation 16

Usability Engineering Lifecycle
Similar to the soft are engineering lifec cle software lifecycle
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 M d l D i i l d
C
t l Model Design includes reengineering the workflow and writing down the application structure li ti t t

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Usability Engineering Lifecycle
Testing and Debugging in Human Computer
Interaction means designing rapid prototypes and users test them
Implementation of the "final" system, delivery and i t ll ti d installation
Evaluation and refinement of the requirements lead to an update of the product, repeating the usability engineering life cycle
 [Mayh99] structured the "Usability Engineering
Lifecycle" into three main sections: Requirements y q
Analysis, Design/Testing/Development, Installation

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Usability Engineering Lifecycle
A less comple model complex The evaluation starts in a very early stage of the development process (paper prototypes…)
Incremental

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Usability Methods

Usability Methods
 User Profiling
 User Persona
 User Scenarios
 Task Analysis
 Prototyping
 Competitive Analysis

 Style Guide g p
 Design Workshops
 Usability Inspection
 Usability Testing
 Quantitative Analyses

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User Profiling
User profiling is described as “ a process of
“…a
gathering all known information about the audience of a specific product, and then g p p breaking them into specific ’profiles’.”
Technology used by these users
Population characteristics (age gender socio
(age, gender, socioeconomic breakdown, etc.)
Relevant experience (in the industry with the industry, technology, etc.)

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User Persona
 A made-up person who represents a centre line made up centre-line view of a particular user profile
 A description of a specific person who i a t d i ti f ifi h is target t user of a system being designed, providing demographic i f d hi information, needs, preferences, ti d f biographical information, and a photo or illustration
 Typically, multiple personas are developed in the early stages of design that represent the spectrum of the target audience

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User Scenarios
 An encapsulated description of an individual user user, using a specific set of computer facilities to achieve a specific outcome under specified circumstances over a certain time interval
 D il use scenario: T k the users are executing
Daily
i Tasks th ti most of the time
 Necessary use scenario: Somewhat necessary to complete the user’s tasks but are not used most of the time g q y  Edge case scenario: Tasks executed infrequently

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Task Analysis
The process of identif ing ho people think identifying how about tasks and how they complete them called task analysis
The goal is make sure that the interface designed matches the users’ mental model of that task closely, … closely so that the users can quickly and easily see what to do at every point

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Prototyping
Prototypes allow
Protot pes allo testing in earl early development stages on a low price and effort and also to test different concepts
Prototypes cut down either on the number of features or the depth of functionality of features to perform usability evaluation as early as possible in the design cycle
Prototypes with different levels of realism, interactivity and production effort can be used 27

Vertical prototyping
Cutting down
C tting do n on the n mber of feat res is number features called vertical prototyping since the result is a narrow system that does include in-depth y, y functionality, but only for a few selected features The exact functionality of a product but for only a small section of the entire product

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Horizontal prototyping
Reducing
Red cing the le el of f nctionalit is called level functionality horizontal prototyping since the result is a surface layer that includes the entire user y interface to a full-featured system but with no underlying functionality
A broad spectrum of the product’s features product s features, but without extensive functionality behind each f function 29

Scenario prototype
A scenario is a mi t re bet een vertical and mixture between ertical horizontal prototypes
In a scenario a specific user task will be demonstrated as real as possible
Different levels of realism

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Competitive Analysis
 A set of methods for getting ideas from the competition, whether through …
reverse-engineering th i user i t f

i i their interface d i rationale, design ti l determining common user interface conventions, or …
finding usability problems that can be fixed

 Results of a competitive analysis can be used in marketing, b d k ti by demonstrating th superior usability t ti the i bilit of your product, or for design, by getting ideas for ways t improve your product to i d t

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Style Guide
 A reference which defines the look and feel of a look-and-feel user interface by clearly setting the standards and conventions of that specific user interface
 Usually include the principles that guide the design of the interface, graphic l f th i t f hi layout grids, exact size t id t i and spacing of elements in the interface, fonts, colors, i t l interactive b h i standard t t ti behavior, t d d text messages (such as error messages), and labeling standards t d d

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Design Workshops
 The developers and the customer come together to increase the usability
 Th d
The development t l t team show d i prototypes h design t t and scenarios and discuss them with the customer
 These workshops provide valuable feedback, which is important especially in early stages of development 33

Usability Inspection
Experts se several techniques
E perts use se eral techniq es for evaluating a user interface by examining and critiquing it
Heuristic Evaluation: Nielsen (2004) defined ten
(
) general principles for user interface design
Guideline Reviews …

Based on experience, psychological principles, a set of previously-defined i i l t f i l d fi d guidelines or using heuristics and judgment

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Heuristic Evaluation
 Visibility of system status
 Match between system and the real world
 User control and freedom
 Consistency and standards
 Error prevention
 Recognition rather than recall
 Flexibility and efficiency of use
 Aesthetic and minimalist design
 Help users recognize, diagnose, and recover from errors  Help and documentation

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To Be Continued …