by : Mark Chambers

Preece et al. define testing or evaluation as the process of 'systematically collecting data that informs us about what it is like for a particular user or group of users to use a product for a particular task in a certain type of environment'. (Preece et al. 2002:317) That is to say that it is a process where the interface is tested against the practices and needs of the user. (Faulkner 1998:109) Evaluation is important in design as it aims to 'eradicate any problems that may be present in a system'. (ibid. 1998:124) Evaluation and amendment of the design at various stages of development helps the designer to verify that the product is suitable for the users' needs, that they can use the product and indeed they like the product. (Preece et al. 2002:317-319) Preece et al. refer to Tognazzini who asserts that evaluation also ensures that the design team focus on 'real problems, not imaginary ones'. (ibid. 2002:321)

Evaluation with users underpins a user-centred approach to design. Preece et al. refer to Gould and Lewis who identify three main characteristics of this approach. There is an 'early focus on users and tasks' which means understanding users and tasks through observation and analysis, whilst actively involving users from the early stages of design. 'Empirical measurement' gauges the performance and reactions of users to storyboards and paper prototypes for example, in the early stages of development and subsequently to software prototypes or simulations for example. Another feature of a user-centred approach is 'iterative design' characterised by cycles of 'design, test, measure and redesign'. (Preece et al. 2002:285)

Some useful links:

Jenny Preece -
Bruce Tognazzini -
Jakob Nielsen -