ISO 09241-11:1998 download free.Ergonomic requirements for office work with visual display terminals (VDTs) — Part 11: Guidance on usability.
The objective of designing and evaluating visual display terminals for usability is to enable users to achieve goals and meet needs in a particular context of use. ISO 9241-11 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.
ISO 9241-11 emphasizes that visual display terminal 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 overall work system. and, when a product is the locus of concern, these measures provide information about Ihe 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 more narrowly to the attributes of a product which make it easier to use (see Annex 0). Requirements and recommendations relating to the attributes of the hardware, software and environment which contribute to visual display terminal usability, and the ergonomic principles underlying them, are provided in other parts of ISO 9241.
ISO 9241-11 defines usability and explains how to identify the information which is necessary to take into account when specifying or evaluating usability of a visual display terminal in terms of measures of user performance and satisfaction. Guidance is given on how to describe the context of use of the product (hardware. software or service) and the relevant measures of usability in an explicit way. The guidance is given in the form of general principles and techniques, rather than in the form of requirements to use specific methods.
The guidance in ISO 9241-11 can be used in procurement, design. development, evaluation, and communication of information about usability. ISO 9241•11 includes guidance on how the usability of a product can be specified and evaluated. It applies both to products intended for general application and products being acquired for or being developed within a specific organization.
ISO 9241-11 also explains how measures of user performance and satisfaction can be used to measure how any component of a work system affects the whole work system in use.
The guidance includes procedures for measuring usability but does not detail all the activities to be undertaken. Specification of detailed user-based methods of measurement is beyond the scope of ISO 9241-11. but further information can be found in Annex B and the bbliography in Annex E.
ISO 9241-11 applies to office work with visual display terminals. It can also apply in other situations where a user is interacting with a product to achieve goals. ISO 9241 parts 12 10 17 provide conditional recommendations which are applicable in specific contexts of use. he guidance in this Part of ISO 9241 can be used in conjunction with ISO 9241 Parts 12 to 17 in order to help identify the applicability of individual recommendations.
ISO 9241-11 focuses on usability and does not provide comprehensive coverage of all objectives of ergonomic design referred to in ISO 6385. However, design for usability will contribute positively to ergonomic objectives, such as the reduction of possible adverse effects of use on human health. safety and performance.
ISO 924 1-11 does not cover the processes of system development. Human-centred design processes for interactive systems are described in ISO 13407.
2 Normative reference
The following standard contains provisions which. through reference in this text. constitute provisions of this part of ISO 9241. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of ISO 9241 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
Relevant characteristics of the users need to be described. These can include knowledge. skill, experience, education. training, physical attributes, and motor and sensory capabilities. It may be necessary to define the characteristics of different types of user. for example users having different levels of experience or performing different roles.
5.3.2 Description of tasks
Tasks are the activities undertaken to achieve a goal. Characteristics of tasks which may influence usability should be described, e.g. the frequency and the duration of the task.
Detailed descriptions of the activities and processes may be required if the description of the context is to be used as a basis for the design or evaluation of details of interaction with the product. This may include description of the allocation of activities and steps between the human and technological resources. Tasks should not be described solely in terms of the functions or features provided by a product or system. Any description of the activities and steps involved in performing the task should be related to the goals which are to be achieved.
For the purposes of evaluating usability, a set of key tasks will typically be selected to represent the significant aspects of the overall task.
NOTE — User tasks and subtasks can be identified by task analysis (for more information see the bibiiography in Annex E).
5.3.3 Description of equipment
Relevant characteristics of the equipment need to be described. The description of the hardware, software and materials associated with a visual display terminal may be in terms of a set 01 products (or System components). one or more of which may be the focus of usability specification or evaluation, or it may be in terms of a set of attributes or performance characteristics of the hardware. software and other materials.
5.3.4 Description of environments
Relevant characteristics of the physical and social environment need to be described Aspects which may need to be described include attributes of the wider technical environment (e.g. the local area network), the physical environment (e.g. workplace. furniture), the ambient environment (e.g. temperature. humidity) and the social and cultural environment (e.g. work practices. organisational structure and attitudes).