DRAFT

INTERNATIONAL ISO DIS 9241-11

STANDARD

September 1994

Guidance on Usability

Editor's note:
This version of the standard will be circulated for international vote terminating in mid-1995. If you have any comments on the content, these can be made formally to your national standards body, or directly to me:
Nigel Bevan
NPL Usability Services
National Physical Laboratory
Teddington, Middlesex
TW11 OLW, UK
Tel: +44 181 943 6993
Fax: +44 181 977 7091
Email: Nigel@hci.npl.co.uk

ISO (the International Organisation for Standardisation) 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 organisations, 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 standardisation.

Draft International Standards adopted by the technical committees are circulated to member bodies for voting. Publication as an international Standard requires approval by at least 75% of the member bodies casting a vote.

International Standard ISO 9241-11 was prepared by the Technical Committee ISO/TC159, Ergonomics, Sub-Committee SC4, Ergonomics of human-system interaction.

ISO 9241 consists of the following Parts, under the general title Ergonomics requirements for office work with visual display terminals (VDTs):

The objective of designing and evaluating for usability is to enable users to achieve goals and meet needs in a particular context of use. This part of ISO 9241 explains the benefits of measuring usability in terms of user performance and satisfaction. These are measured by the extent to which the intended goals of use are achieved, the resources that have to be expended to achieve the intended goals, and the extent to which the user finds the use of the product acceptable.

This part emphasises that usability is dependent on the context of use and that the level of usability achieved will depend on the specific circumstances in which a product is used. The context of use consists of the users, tasks, equipment (hardware, software and materials), and the physical and social environments which may all influence the usability of a product in a work system. Measures of user performance and satisfaction assess the quality of the work system in use, and, when a product is the focus of concern, these measures provide information about the usability of that product in the particular context of use provided by the rest of the work system. The effects of changes in other components of the work system, such as the amount of user training, or the improvement of the lighting, can also be measured by user performance and satisfaction.

The term usability is sometimes used to refer to the attributes of a product which make it easier to use (see Annex D). Requirements and recommendations relating to the attributes of the hardware, software and environment which contribute to usability, and the ergonomic principles underlying them, are provided in other parts of ISO 9241. This part of ISO 9241 explains how the resulting usability of a product when used in a particular context can be assessed by measures of user performance and satisfaction.

DRAFT INTERNATIONAL STANDARD ISO DIS 9241-11: 1994 (E)

Guidance on Usability

• 1. Scope(This part of ISO 9241 defines usability and explains how to identify the information which is necessary to take into account when specifying or evaluating usability in terms of measures of user performance and satisfaction. )
• 2. Normative references(The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO 9241.)
• 3. Definitions(For the purposes of this part of ISO 9241, the following definitions apply...)
• 4. Benefits and rationale(Usability is an important consideration in the design of products because it is concerned with the extent to which the users of products are able to work effectively, efficiently and with satisfaction.)
• 5. Specifying and measuring the usability of products(Framework for specifying usa, Context of use, Usability measures, Interpretation of measures...)
• 6. Specification and evaluation of usability during design(Specification of overall requirements for a product, Specification of usability requirements for a product, Product development, Specification or evaluation of product attributes, Usability measurement, Quality system)
• 7. Specifying and measuring the quality of a work system in use(Relationship to usability, Examples of application)
• Annex A (informative)(Example of how to specify the context of use)
• Annex B (informative)(Examples of usability measures)
• Annex C (informative)(Example of a usability requirements specification)
• Annex D (informative)(Relationship to other standards)
• Annex E (informative)(References and bibliography)