EN ISO 9241-11:2018

Ergonomics of human-system interaction - Part 11: Usability: Definitions and concepts (ISO 9241-11:2018)

ISO 9241-11:2018 provides a framework for understanding the concept of usability and applying it to situations where people use interactive systems, and other types of systems (including built environments), and products (including industrial and consumer products) and services (including technical and personal services).
NOTE       In this document, the phrase "object of interest" refers to the system, product or service for which usability is being considered (see 8.1).
ISO 9241-11:2018:
-      explains that usability is an outcome of use;
-      defines key terms and concepts;
-      identifies the fundamentals of usability; and
-      explains the application of the concept of usability.
ISO 9241-11:2018 does not describe specific processes or methods for taking account of usability in design development or evaluation.
The intended users of this document include:
-      usability/ergonomics/human factors professionals;
-      designers and developers of systems, products and services;
-      quality assurance personnel;
-      public and corporate purchasers; and
-      consumer organizations.
The most common applications of this document are in design and evaluation.

Ergonomie der Mensch-System-Interaktion - Teil 11: Gebrauchstauglichkeit: Begriffe und Konzepte (ISO 9241-11:2018)

Dieses Dokument liefert einen Rahmen für das Verständnis des Konzepts der Gebrauchstauglichkeit und für dessen Anwendung auf interaktive und andere Systeme (einschließlich gebaute Umwelt), Produkte (einschließlich Industrie- und Konsumgüter) und Dienstleistungen (einschließlich technischer und persönlicher Dienstleistungen).
ANMERKUNG In diesem Dokument bezieht sich die Formulierung „Betrachtungsgegenstand“ auf das System, Produkt oder die Dienstleistung, für die die Gebrauchstauglichkeit betrachtet wird (siehe 8.1).
Dieses Dokument:
- erklärt, dass Gebrauchstauglichkeit ein Ergebnis der Nutzung ist;
- definiert Schlüsselbegriffe und Konzepte;
- identifiziert die Grundsätze der Gebrauchstauglichkeit; und
- erläutert die Anwendung des Konzepts der Gebrauchstauglichkeit.
Dieses Dokument beschreibt keine spezifischen Prozesse oder Verfahren für die Berücksichtigung der Gebrauchstauglichkeit bei der Gestaltungsentwicklung oder der Evaluierung.
Vorgesehene Benutzer dieses Dokuments sind u. a.:
- Fachkräfte für Gebrauchstauglichkeit / Ergonomie / Arbeitswissenschaft;
- Planer und Entwickler von Systemen, Produkten und Dienstleistungen;
- Personal aus dem Bereich Qualitätssicherung;
- Einkäufer für öffentliche Einrichtungen und Unternehmen; und
- Verbraucherorganisationen.
Dieses Dokument findet vor allem in den Bereichen Gestaltung und Evaluierung seine Anwendung.

Ergonomie de l'interaction homme-système - Partie 11: Utilisabilité - Définitions et concepts (ISO 9241-11:2018)

ISO 9241-11:2018 fournit un cadre pour comprendre le concept d'utilisabilité et l'appliquer à des situations où des personnes utilisent des systèmes interactifs, et d'autres types de systèmes (y compris des environnements bâtis), des produits (y compris des produits industriels et de grande consommation) et des services (y compris des services techniques et personnels).
NOTE       Dans le présent document, l'expression «objet d'intérêt» se rapporte au système, produit ou service pour lequel l'utilisabilité est déterminée (voir 8.1).
ISO 9241-11:2018:
-      explique que l'utilisabilité est un résultat de l'utilisation,
-      définit les termes et concepts clés,
-      identifie les principes fondamentaux de l'utilisabilité, et
-      explique l'application du concept d'utilisabilité.
ISO 9241-11:2018 ne décrit pas de processus ou de méthodes spécifiques pour prendre en compte l'utilisabilité dans le développement ou l'évaluation de la conception.
Les utilisateurs cibles du présent document comprennent
-      les professionnels de l'utilisabilité/de l'ergonomie/des facteurs humains,
-      les concepteurs et développeurs de systèmes, produits et services,
-      le personnel en charge de l'assurance qualité,
-      les acheteurs des secteurs public et privé, et
-      les organisations de consommateurs.
Les applications les plus courantes du présent document concernent la conception et l'évaluation.

Ergonomija medsebojnega vpliva človek-sistem - 11. del: Uporaba: Definicije in pojmi (ISO 9241-11:2018)

Ta dokument ponuja okvir za razumevanje koncepta uporabnosti ter njegovo uporabo v situacijah, v katerih ljudje uporabljajo interaktivne sisteme in druge vrste sistemov (vključno z grajenimi okolji), izdelke (vključno z industrijskimi in potrošniškimi izdelki) in storitve (vključno s tehničnimi in osebnimi storitvami).
OPOMBA V tem dokumentu fraza »interesni predmet» pomeni sistem, izdelek ali storitev, pri katerem se presoja o uporabnosti (glejte 8.1).
Ta dokument:
– razlaga, da je uporabnost rezultat uporabe;
– določa ključne izraze in koncepte;
– navaja osnove uporabnosti; in
– razlaga uporabo koncepta uporabnosti.
Ne opisuje posebnih postopkov ali metod za upoštevanje uporabnosti pri razvoju in ocenjevanju načrtovanja.
Predvideni uporabniki tega dokumenta:
– strokovnjaki s področja uporabnosti/ergonomije/človeških dejavnikov;
– oblikovalci in razvijalci sistemov, izdelkov in storitev;
– osebje za zagotavljanje kakovosti;
– javni in korporativni naročniki;
– potrošniške organizacije.
Ta dokument se najpogosteje uporablja pri oblikovanju in ocenjevanju.

General Information

• Status: Published
• Publication Date: 29-May-2018
• Withdrawal Date: 29-Nov-2018
• ICS: 13.180 - Ergonomics
• ICS: 35.080 - Software
• ICS: 35.180 - IT Terminal and other peripheral equipment
• Technical Committee: CEN/TC 122 - Ergonomics
• Drafting Committee: CEN/TC 122/WG 5 - Ergonomics of human-computer interaction
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 30-May-2018
• Completion Date: 30-May-2018
• Ref Project: SIST EN ISO 9241-11:2018 - Ergonomics of human-system interaction - Part 11: Usability: Definitions and concepts (ISO 9241-11:2018)

Relations

• Replaces: EN ISO 9241-11:1998 - Ergonomic requirements for office work with visual display terminals (VDTs) - Part 11: Guidance on usability (ISO 9241-11:1998)
• Effective Date: 28-Aug-2013

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2018
1DGRPHãþD
SIST EN ISO 9241-11:2001
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SRMPL,62
Ergonomics of human-system interaction - Part 11: Usability: Definitions and concepts
(ISO 9241-11:2018)
Ergonomie der Mensch-System-Interaktion - Teil 11: Gebrauchstauglichkeit: Begriffe und
Konzepte (ISO 9241-11:2018)
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Ta slovenski standard je istoveten z: EN ISO 9241-11:2018
ICS:
13.180 Ergonomija Ergonomics
35.180 Terminalska in druga IT Terminal and other
periferna oprema IT peripheral equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 9241-11
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2018
EUROPÄISCHE NORM
ICS 13.180; 35.080 Supersedes EN ISO 9241-11:1998
English Version
Ergonomics of human-system interaction - Part 11:
Usability: Definitions and concepts (ISO 9241-11:2018)
Ergonomie de l'interaction homme-système - Partie Ergonomie der Mensch-System-Interaktion - Teil 11:
11: Utilisabilité - Définitions et concepts (ISO 9241- Gebrauchstauglichkeit: Begriffe und Konzepte (ISO
11:2018) 9241-11:2018)
This European Standard was approved by CEN on 15 December 2017.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9241-11:2018 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 9241-11:2018) has been prepared by Technical Committee ISO/TC 159
"Ergonomics" in collaboration with Technical Committee e CEN/TC 122 “Ergonomics” the secretariat of
which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by November 2018, and conflicting national standards
shall be withdrawn at the latest by November 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 9241-11:1998.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 9241-11:2018 has been approved by CEN as EN ISO 9241-11:2018 without any
modification.
INTERNATIONAL ISO
STANDARD 9241-11
Second edition
2018-03
Ergonomics of human-system
interaction —
Part 11:
Usability: Definitions and concepts
Ergonomie de l'interaction homme-système —
Partie 11: Utilisabilité — Définitions et concepts
Reference number
ISO 9241-11:2018(E)
©
ISO 2018
ISO 9241-11:2018(E)
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

ISO 9241-11:2018(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Rationale and benefits of usability . 6
5 Usability in a context of use. 6
5.1 Concept of usability . 6
5.2 System, product or service. 8
5.3 Consideration of usability for “specified” circumstances . 8
5.3.1 General. 8
5.3.2 Specified users . 8
5.3.3 Specified goals. 8
5.3.4 Specified contexts of use . 8
6 Outcomes of use. 9
6.1 Usability as an outcome . 9
6.2 Effectiveness . 9
6.2.1 General. 9
6.2.2 Accuracy . 9
6.2.3 Completeness .10
6.3 Efficiency .10
6.3.1 General.10
6.3.2 Time used .11
6.3.3 Human effort expended .11
6.3.4 Financial resources expended .11
6.3.5 Materials expended .11
6.4 Satisfaction .11
6.4.1 General.11
6.4.2 Physical responses .11
6.4.3 Cognitive responses .12
6.4.4 Emotional responses .12
6.5 Specific uses of the concept of usability .12
6.6 Other outcomes of use .12
6.6.1 General.12
6.6.2 Accessibility .12
6.6.3 User experience .13
6.6.4 Avoidance of harm from use .13
7 Context of use .13
7.1 Components of the context of use .13
7.2 Users within the context of use .14
7.3 Goals within the context of use .14
7.4 Tasks within the context of use .15
7.5 Resources .16
7.5.1 General.16
7.5.2 Reusable resources .16
7.5.3 Expendable resources .16
7.6 Environment .16
7.6.1 General.16
7.6.2 Technical environment .16
7.6.3 Physical environment .17
7.6.4 Social, cultural and organizational environment .17
ISO 9241-11:2018(E)
8 Applying the concept of usability .17
8.1 Usability that results from use of various objects of interest .17
8.2 Characteristics of users, tasks and environments needed for usability .18
8.3 Achieving usability in design and development .18
8.4 Usability in procurement .19
8.5 Usability in a review or when making a comparison .19
8.6 Usability inputs to marketing and market research .19
Annex A (informative) Relationship of usability to other concepts .20
Annex B (informative) Usability measurement .25
Bibliography .28
iv © ISO 2018 – All rights reserved

ISO 9241-11:2018(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 159 Ergonomics, Subcommittee SC 4,
Ergonomics of human-system interaction.
This second edition cancels and replaces the first edition (ISO 9241-11:1998), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the scope has been extended to include systems and services (consistent with other parts of ISO 9241
including ISO 9241-210, and with ISO 26800 and ISO 20282);
— a wider range of goals is considered, including personal outcomes and organizational outcomes;
— efficiency has been defined in relation to the results achieved rather than in relation to accuracy and
completeness with which users achieve goals.;
— satisfaction has been clarified to include a wider range of issues.
A list of all parts in the ISO 9241 series can be found on the ISO website.
ISO 9241-11:2018(E)
Introduction
The objective of designing and evaluating systems, products and services for usability is to enable users
to achieve goals effectively, efficiently and with satisfaction, taking account of the context of use. This
document explains how usability can be interpreted in terms of user performance and satisfaction, and
emphasizes that usability is dependent on the specific circumstances in which a system, product or
service is used.
This document explains how to interpret each component in the definition of usability: “the extent
to which a system, product or service can be used by specified users to achieve specified goals with
effectiveness, efficiency and satisfaction in a specified context of use”.
NOTE 1 In this document, usability relates to the outcome of interacting with a system, product or service.
Usability, as defined in this document, is not an attribute of a product, although appropriate product attributes
can contribute to the product being usable in a particular context of use.
NOTE 2 Usability is a more comprehensive concept than is commonly understood by “ease-of-use” or “user
friendliness”.
Usability is relevant to:
— regular ongoing use, to enable users to achieve their goals effectively, efficiently and with satisfaction;
— learning, to enable new users to be become effective, efficient and satisfied when starting to use a
system, product or service;
— infrequent use, to enable users to be effective, efficient and satisfied, with the system on each reuse;
— use by people with the widest range of capabilities;
— minimizing the risk and the undesirable consequences of use errors; and
— maintenance, in that it enables maintenance tasks to be completed effectively, efficiently and with
satisfaction.
Usability is relevant when designing or evaluating interactions with a system, product or service for the
purposes of:
— development;
— procurement;
— review or comparison; and
— marketing and market research.
Annexes A and B in this document give an explanation of the relationship of usability to other concepts
and disciplines such as human-centred design, ergonomics, human factors, human-centred quality, user
experience and quality (as used in systems and software engineering), and explain how usability can
be considered for different scopes of contexts of use and provide examples of usability measures.
vi © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 9241-11:2018(E)
Ergonomics of human-system interaction —
Part 11:
Usability: Definitions and concepts
1 Scope
This document provides a framework for understanding the concept of usability and applying it
to situations where people use interactive systems, and other types of systems (including built
environments), and products (including industrial and consumer products) and services (including
technical and personal services).
NOTE In this document, the phrase “object of interest” refers to the system, product or service for which
usability is being considered (see 8.1).
This document:
— explains that usability is an outcome of use;
— defines key terms and concepts;
— identifies the fundamentals of usability; and
— explains the application of the concept of usability.
It does not describe specific processes or methods for taking account of usability in design development
or evaluation.
The intended users of this document include:
— usability/ergonomics/human factors professionals;
— designers and developers of systems, products and services;
— quality assurance personnel;
— public and corporate purchasers; and
— consumer organizations.
The most common applications of this document are in design and evaluation.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
ISO 9241-11:2018(E)
3.1 Usability
3.1.1
usability
extent to which a system, product or service can be used by specified users to achieve specified goals
with effectiveness, efficiency and satisfaction in a specified context of use
Note 1 to entry: The “specified” users, goals and context of use refer to the particular combination of users, goals
and context of use for which usability is being considered.
Note 2 to entry: The word “usability” is also used as a qualifier to refer to the design knowledge, competencies,
activities and design attributes that contribute to usability, such as usability expertise, usability professional,
usability engineering, usability method, usability evaluation, usability heuristic.
[SOURCE: ISO 9241-210:2010, 2.13, modified — Notes 1 and 2 were added.]
3.1.2
product
item that is made or created by a person or machine
3.1.3
consumer product
product that is intended to be acquired and used by an individual for personal rather than
professional use
[SOURCE: ISO 20282-1:2006, 3.2]
3.1.4
system
combination of interacting elements organized to achieve one or more stated purposes
Note 1 to entry: A system is sometimes considered as a product or as the services it provides.
Note 2 to entry: A complete system includes all of the associated equipment, facilities, material, computer
programs, firmware, technical documentation, services and personnel required for operations and support to
the degree necessary for self-sufficient use in its intended environment.
Note 3 to entry: A system can be composed of a product, service, built environment or combination thereof,
and people.
[SOURCE: ISO/IEC 15288:2015, 4.1.46, modified — Notes 2 and 3 have been replaced.]
3.1.5
interactive system
combination of hardware and/or software and/or services and/or people that users interact with in
order to achieve specific goals
Note 1 to entry: This includes, where appropriate, packaging, user documentation, on-line and human help,
support and training.
[SOURCE: ISO 9241-210:2010, 2.8, modified]
3.1.6
service
means of delivering value for the customer by facilitating results the customer wants to achieve
Note 1 to entry: Services can include both human-system interactions (e.g. accessing a word processor through
the web) and human-human interactions (e.g. a citizen interacting with a clerk at the post office counter).
Note 2 to entry: The “customer” is a user, and does not necessarily have a financial relationship.
[SOURCE: ISO/IEC 20000-1:2011, 3.26, modified — The notes have been replaced.]
2 © ISO 2018 – All rights reserved

ISO 9241-11:2018(E)
3.1.7
user
person who interacts with a system, product or service
Note 1 to entry: Users of a system, product or service include people who operate the system, people who make
use of the output of the system and people who support the system (including providing maintenance and
training).
[SOURCE: ISO 26800:2011, 2.10, modified — Note 1 has been replaced and Notes 2 and 3 were deleted.]
3.1.8
user group
subset of intended users who are differentiated from other intended users by characteristics of the
users, tasks or environments that could influence usability
[SOURCE: ISO/TS 20282-2:2013, 4.24, modified — The wording of the definition has been modified and
the note omitted.]
3.1.9
stakeholder
person or organization that can affect, be affected by, or perceive themselves to be affected by a decision
or activity
Note 1 to entry: Stakeholders can include: users, purchasers, systems owners or managers and people who are
indirectly affected by the operation of a system, product or service.
Note 2 to entry: Different stakeholders can have different needs, requirements or expectations.
[SOURCE: ISO 31000:2009, 2.13, modified — The original note has been replaced by Notes 1 and 2.]
3.1.10
goal
intended outcome
3.1.11
task
set of activities undertaken in order to achieve a specific goal
Note 1 to entry: These activities can be physical, perceptual and/or cognitive.
Note 2 to entry: While goals are independent of the means used to achieve them, tasks describe particular means
of achieving goals.
3.1.12
effectiveness
accuracy and completeness with which users achieve specified goals
3.1.13
efficiency
resources used in relation to the results achieved
Note 1 to entry: Typical resources include time, human effort, costs and materials.
3.1.14
satisfaction
extent to which the user's physical, cognitive and emotional responses that result from the use of a
system, product or service meet the user’s needs and expectations
Note 1 to entry: Satisfaction includes the extent to which the user experience that results from actual use meets
the user’s needs and expectations.
Note 2 to entry: Anticipated use can influence satisfaction with actual use.
ISO 9241-11:2018(E)
3.1.15
context of use
combination of users, goals and tasks, resources, and environment
Note 1 to entry: The “environment” in a context of use includes the technical, physical, social, cultural and
organizational environments.
3.2 Related concepts and disciplines
3.2.1
human-centred quality
extent to which requirements for usability, accessibility, user experience and avoidance of harm from
use are met
Note 1 to entry: Provision of the necessary technical functionality is a prerequisite for human-centred quality.
Note 2 to entry: Usability, accessibility, user experience and avoidance of harm from use can only be managed to
the extent that they can be controlled by designed aspects of the interactive system.
Note 3 to entry: Human-centred quality is a collective term for the intended outcomes of interaction of the user
with the system.
1)
[SOURCE: ISO 9241-220:— , 3.11]
3.2.2
accessibility
extent to which products, systems, services, environments and facilities can be used by people from a
population with the widest range of user needs, characteristics and capabilities to achieve identified
goals in identified contexts of use
Note 1 to entry: Context of use includes direct use or use supported by assistive technologies.
3.2.3
user experience
user’s perceptions and responses that result from the use and/or anticipated use of a system, product
or service
Note 1 to entry: Users’ perceptions and responses include the users’ emotions, beliefs, preferences, perceptions,
comfort, behaviours, and accomplishments that occur before, during and after use.
Note 2 to entry: User experience is a consequence of brand image, presentation, functionality, system
performance, interactive behaviour, and assistive capabilities of a system, product or service. It also results from
the user’s internal and physical state resulting from prior experiences, attitudes, skills, abilities and personality;
and from the context of use.
Note 3 to entry: The term "user experience" can also be used to refer to competence or processes such as user
experience professional, user experience design, user experience method, user experience evaluation, user
experience research, user experience department.
Note 4 to entry: Human-centred design can only manage those aspects of user experience that result from
designed aspects of the interactive system.
[SOURCE: ISO 9241-210:2010, 2.15, modified — The definition has been reworded for clarification, Note
3 to entry has been replaced and Note 4 to entry has been added.]
3.2.4
harm from use
negative consequences regarding health, safety, finances or the environment that result from use of
the system
Note 1 to entry: The negative consequences can be for the user or for any other stakeholder.
1) Under preparation. (Stage at the time of publication: ISO/FDIS 9241-220.)
4 © ISO 2018 – All rights reserved

ISO 9241-11:2018(E)
[SOURCE: ISO 9241-220:—, 3.9]
3.2.5
ergonomics
human factors
scientific discipline concerned with the understanding of interactions among human and other elements
of a system, and the profession that applies theory, principles, data and methods to design in order to
optimize human well-being and overall system performance
[SOURCE: ISO 26800:2011, 2.2, modified — The note has been omitted.]
3.2.6
human-centred design
HCD
approach to system design and development that aims to make interactive systems more usable by
focussing on the use of the system; applying human factors, ergonomics and usability knowledge and
techniques
Note 1 to entry: The term “human-centred design” is used rather than “user-centred design” in order to emphasize
that this document also addresses impacts on a number of stakeholders, not just those typically considered as
users. However, in practice, these terms are often used synonymously.
Note 2 to entry: Usable systems can provide a number of benefits including improved productivity, enhanced
user well-being, avoidance of stress, increased accessibility, and reduced risk of harm.
[SOURCE: ISO 9241-210:2010, 2.7, modified]
3.3 Other definitions
3.3.1
built environment
external and internal environments and any element, component or fitting that is commissioned,
designed, constructed and managed for use by people
[SOURCE: ISO 21542:2011, 3.10]
3.3.2
requirement
condition or capability that must be met or possessed by a system, system component, product, or
service to satisfy an agreement, standard, specification, or other formally imposed documents
[SOURCE: ISO/IEC 24765:2010, 3.2506 definition 2, modified — The note has been omitted.]
3.3.3
use error
user action or lack of user action while using the system, product or service that leads to a different
result than that intended by the manufacturer or expected by the user
Note 1 to entry: Use error includes the inability of the user to complete a task.
Note 2 to entry: Use errors can result from a mismatch between the characteristics of the user, user interface,
task, or use environment.
Note 3 to entry: Users might be aware or unaware that a use error has occurred.
Note 4 to entry: A malfunction of an interactive system that causes an unexpected result is not considered a
use error.
Note 5 to entry: The term use error is used in preference to user error or human error in order to avoid the
implied assignment of responsibility for the error to the user.
ISO 9241-11:2018(E)
[SOURCE: IEC 62366-1:2015, 3.21, modified — The term medical device was replaced by interactive
system, Notes 4 and 5 have been replaced and Note 6 was omitted.]
4 Rationale and benefits of usability
Usability is the effectiveness, efficiency and satisfaction of the user’s interaction with the object of
interest.
When designing a system, product or service:
— where usability is lower than expected, the intended users might not be able or willing to use the
system, product or service;
— where usability is sufficient, the system, product or service will provide the intended personal,
social and economic benefits for users, employers and suppliers;
— where usability is higher than expected, the system, product or service can have a competitive
advantage (e.g. customer retention, or customers who are willing to pay a premium).
Specific benefits provided by appropriate usability include the following:
— contributing to meeting targets for the operational efficiency of organizations;
— making systems, products and services easier to understand and to learn how to use, thus increasing
uptake and reducing support costs such as help desks;
— increasing usability for people with a wider range of capabilities (see 6.6.2);
— improving the user experience (see 6.6.3);
— contributing towards sustainability objectives (see ISO 26000 and ISO 27500);
— reducing the risks of the undesirable personal, social or business consequences (see A.6.4);
— providing a competitive advantage, for example by improving brand image.
This document provides a basis for identifying the relevant components of effectiveness, efficiency and
satisfaction, and the components of the context of use. When specifying, designing or evaluating the
usability that results from use of a system, product or service, the objective is to achieve the intended
level of effectiveness, efficiency and satisfaction. The estimation of the potential impacts of particular
levels of usability (whether these are business, organizational, personal or social impacts) can be used
to justify the development efforts needed (see ISO 9241-210 and ISO 9241-220).
NOTE Reference[32] provides information on cost-justification of the development effort for usability.
5 Usability in a context of use
5.1 Concept of usability
Usability is the extent to which a system, product or service can be used by specified users to achieve
specified goals with effectiveness, efficiency and satisfaction in a specified context of use.
Figure 1 shows the system, product or service, which represents the object of interest. The object
of interest is shown within the context of use, which is composed of the users, the goals and tasks,
the resources, and the environment. Usability, which is composed of effectiveness, efficiency and
satisfaction, is shown as an outcome of use. There are also other outcomes of use that include
accessibility, user experience and avoidance of harm from use.
NOTE The components of usability are described in detail in 6.2, 6.3, and 6.4, and the other outcomes in 6.6.
6 © ISO 2018 – All rights reserved

ISO 9241-11:2018(E)
Outcomes of Use
Context of use
Usability
Users
Effectiveness
Eficiency
System,
Goals
Product,
Environment and Satisfaction
or
Tasks
Service
Other outcomes
• Accessibility
• User experience
• Avoidance of harm
Resources
from use
• etc.
Figure 1 — Usability that results from use of a system, product or service in a context of use
The extent to which usability is achieved will vary depending on the characteristics of:
— the system, product or service;
— the goals;
— the tasks;
— the users;
— the resources;
— the use environment.
Use of the same system, product or service can result in significantly different levels of usability
depending on the goals, the types of users and other components of the context of use. Usability will
be influenced by the users’ characteristics, capabilities and other individual differences, and by the
characteristics of the tasks that they perform, and can depend on the physical, social, cultural and
organizational environments.
Usability is typically considered in relation to a system, product or service that is being designed or
evaluated in a given context of use (i.e. for given user groups, tasks and environment).
EXAMPLE 1 A software application that supports advanced statistical analyses has high levels of usability for
experienced statisticians, but has low levels of usability for students taking a first year statistics module.
Usability can also be used to consider the suitability of a component of the context of use (see 8.2).
EXAMPLE 2 The level of ambient lighting (part of physical environment) needed for a specific product to be
usable in an (otherwise) specified context of use.
There is no single intrinsic measure of the usability of a system, product or service because effectiveness,
efficiency and satisfaction depend on the users, goals and other components of the context of use for
which usability is being considered.
ISO 9241-11:2018(E)
5.2 System, product or service
Usability is considered in relation to an identified object of interest (a system, product or service).
Systems, products or services can be considered at various levels of specificity from highly complex
systems to individual parts of a system, product or service.
NOTE 1 Usability results from interaction between a user and an object of interest. The object of interest with
which the user interacts (e.g. a system or service) can include other people.
NOTE 2 Different objects of interest to which the concept of usability can be applied are discussed in 8.1.
5.3 Consideration of usability for “specified” circumstances
5.3.1 General
The “specified” users, goals and other aspects of the context of use refer to the particular combination
of users, goals and other aspects of the context of use that are “specified” for the purpose of considering
the usability that results from use of an identified object of interest.
NOTE 1 Users, goals, and other aspects of the context of use can be “specified” for purposes of considering
usability, whether or not they have been considered in the specifications that were used for purposes of systems
development.
NOTE 2 The usability that results from use of an object of interest can be significantly different for different
combinations of specified users, goals and tasks, resources and environments.
5.3.2 Specified users
The “specified” users are the users who are identified for the purpose of considering usability. The
characteristics of the users will influence usability (see 7.2).
NOTE The specified users are one or more user groups that are typically, but not necessarily, part of the set
of intended groups of users for whom the system, product or service was developed.
5.3.3 Specified goals
It is important to clearly identify the “specified” goals for which usability is being considered, because
not all identified goals might be selected to be specified goals (see 7.3).
The specified goals (intended outcomes) for which usability is considered, could be those intended by
the user, by the management or by the manufacturer.
NOTE 1 In many situations, usability is considered for a set of goals rather than only for a single goal.
NOTE 2 There can be conflicts between goals that will result in a trade-off between achieving usability for one
specified goal with achieving usability for another specified goal.
EXAMPLE When booking a ticket for travel, there could be conflicts between the goal to have the shortest
travel time, the goal to be comfortable, the goal to pay the lowest price, and the goal to configure the trip in detail.
5.3.4 Specified contexts of use
It is important to clearly identify the “specified contexts of use” for which usability is being considered.
The “specified” contexts of use are typically a subset of all possible combinations of contexts of use.
8 © ISO 2018 – All rights reserved

ISO 9241-11:2018(E)
6 Outcomes of use
6.1 Usability as an outcome
Usability focuses on the effectiveness, efficiency and satisfaction of the user’s interaction with the
object of interest.
Effectiveness (see 6.2), efficiency (see 6.3) and satisfaction (see 6.4) are each composed of more specific
components.
The relative importance of effectiveness, efficiency and satisfaction and their components will depend
on the reason that usability is being considered and the specified context of use.
EXAMPLE For a trained clinical user of a medical device, the most important considerations might be
effectiveness (accuracy and completeness) and efficiency (time used).
NOTE 1 The user could be effective without being efficient or satisfied, or satisfied without being effective or
efficient.
NOTE 2 Provision of the necessary technical functionality is a prerequisite for usability.
NOTE 3 Effectiveness, efficiency and satisfaction can each be considered, specified or evaluated as measu
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