Recommended methods: Specialised methods
The recommended methods were selected as generally applicable and easy to learn and apply, even in organisations with limited usability skills.
The recommended methods assume that the requirements are well-understood. If this is not the case, additional methods such as focus groups, observing users in field studies, task analysis and task allocation should be used.
Where appropriate skills are available, user-based evaluation should be complemented by expert and heuristic evaluation.
These and other more specialised methods are described below.
This technique is a means of defining and managing the user-centred design activities that will take place during the development of a product or system. For each activity a task manager is appointed, an appropriate technique is selected and a schedule is specified. The usability plan is a living document, and undergoes regular reviews as the project progresses.
A focus group brings together a cross-section of stakeholders in the context of a facilitated but informal discussion group. Views are elicited by the facilitator on topics of relevance to the software product being evaluated. Focus groups are often used to identify initial requirements they can also serve as a means of collecting feedback once a system has been in use or has been placed on field trials for some time. Focus groups give more limited information than a field study or user-based evaluation, and focus groups should not be used to replace evaluation by individual users.
Whenever possible, the design team should arrange a field study to observe how users currently work. This can provide an in depth understanding of the users needs and working environment, and provide a solid foundation for design. This information is often difficult or impossible to obtain by any other means.
A functionality matrix can be used to specify the system functions that each user will require for the different tasks that they perform. The most critical task functions are identified so that more time can be paid to them during usability testing later in the design process. This method is useful for systems where the number of possible functions is high (e.g. in a generic software package) and where the range of tasks that the user will perform is well specified. In these situations, the functionality matrix can be used to trade-off different functions, or to add and remove functions depending on their value for supporting specific tasks. It is also useful for multi-user systems to ensure that the tasks of each user type are supported.
Storyboards are sequences of images which demonstrate the relationship between individual events (e.g. screen outputs) and actions within a system. A typical storyboard will contain a number of images depicting features such as menus, dialogue boxes and windows. The formation of these screen representations into a sequence conveys further information regarding the possible structures, functionality and navigation options available. The storyboard can be shown to colleagues in a design team as well as potential users, allowing others to visualise the composition and scope of possible
Task analysis is used to identify what a user is required to do in terms of actions and/or cognitive processes to achieve a task. A detailed task analysis can be conducted to understand the current system and the information flows within it. These information flows are important to the maintenance of the existing system and must be incorporated or substituted in any new system. Task analysis makes it possible to design and allocate tasks appropriately within the new system. The functions to be included within the system and the user interface can then be accurately specified. For simple systems, tasks can be identified by questioning users, and tasks can be sorted and grouped using post-it-notes. For more complex systems a more structured method may be beneficial.
A successful system depends on the effective allocation of tasks between the system and the users. Different task allocation options may need to be considered before specifying a clear system boundary. A range of options are established to identify the optimal division of labour, to provide job satisfaction and efficient operation of the whole work process. The approach is most useful for systems which affect whole work processes rather than single user, single task products.
Expert evaluation involves a usability expert inspecting a system to identify any usability problems. Further information on appropriate methods such as heuristic evaluation can be found in the INUSE Handbook.
ISO 9241 applicability workshop
This is a participatory technique in which designers attend a workshop with analysts and HCI specialists (who act as facilitators) to examine the ergonomic issues associated with the system being developed and scope the work required to develop solutions based on the contents of the ISO 9241 standard. This standard contains the best and most widely agreed body of software ergonomics advice. In particular the processes recommended in Part 1 and Annex 1 of parts 12-17 of the standard ensure a systematic evaluation of each clause to check its applicability to the particular system(s) under consideration. The combination of these processes and recommendations is used to ensure that the principles of software ergonomics have been considered in the development of a system. This approach supports (and may supersede) the use of style guides.
ISO 9241 Software conformity assessment
The method ensures that a product conforms with ISO 9241 and thus embodies good ergonomic principles. A software product is assessed for conformance to the relevant requirements as detailed in the ISO 9241 standard: Ergonomic Requirements for work with Visual Display Terminals (VDTs). Developers provide documentary evidence regarding their processes and one or more auditors examine these documents and interview relevant staff.
This method allows designers to create a video-based simulation of interface functionality using simple materials and equipment. As with paper-prototyping, interface elements are created using paper, pens, acetates etc. Video equipment is then used to film the functionality of the interface. For example a start state for the interface is recorded using a standard camcorder. The movements of a mouse pointer over menus may then be simulated by stopping and starting the camcorder as interface elements are moved, taken away and added. Users do not directly interact with the prototype in this approach, however they can view and comment on the completed video-based simulation. This variant on paper-prototyping is particularly suited for simulating the dynamic character of a simple interface mock-up and can be used during the early stages of the design cycle to demonstrate design options and concepts to an audience.
This variant of computer-based prototyping involves a user interacting with a computer system which is actually operated by a hidden developer - referred to as the 'wizard'. The wizard processes input from a user and simulates system output. During this process the user is led to believe that they are interacting directly with the system. This form of prototyping is beneficial early on in the design cycle and provides a means of studying a user's expectations and requirements. The approach is particularly suited to exploring design possibilities in systems which are demanding to implement such as those that feature intelligent interfaces incorporating agents, advisors and/or natural language processing.
It is often helpful to develop possible system concepts with a parallel process in which several different designers work out possible designs. The aim is to develop and evaluate different system ideas before settling on a single approach as a basis for the system. When designers have completed their designs, it is likely that they will have approached the problem in radically different ways that will give rise to different user systems. It is then possible to combine designs and take the best features from each. Parallel design is most useful for novel systems where they is no established guidelines for how best the system should operate. Although parallel design might at first seem like an expensive approach, since many ideas are generated without implementing them, it is a very cheap way of exploring the range of possible system concepts and selecting the probable optimum.
The measurement of cognitive workload involves assessing how much mental effort a user expends whilst using a product to accomplish a task. This information can be obtained by a number of means such as the subjective workload assessment technique which is based on three rating scale dimensions: time load, mental effort load and psychological stress load. There are also questionnaires for evaluating subjective perceptions of effort. Cognitive workload complements other subjective measures, and is particularly useful information when the user is expected to be over- or under-loaded.
MUSiC: Measuring the Usability of Systems in Context
User performance measurement method
This is a detailed procedure for usability testing that provides reliable metrics for effectiveness and efficiency as defined in ISO 9241-11. It includes a procedure for scoring effectiveness based on the impact of errors and omissions. An overview is contained in the paper The MUSiC Performance Measurement Method (133K). The complete handbook(1Mb) is also available.
(Note that the DRUM tool for video analysis is no longer available, but similar commercial tools are now available from suppliers such as Noldus.)
Copyright © 2002 Serco Ltd. Reproduction permitted provided the source is acknowledged.