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Designing useful and attractive products requires skill and creativity. As products evolve from initial ideas through conceptual design and prototypes, iterative cycles of design and evaluation help to ensure that they meet users’ needs. Deciding when and how to evaluate
a product requires careful consideration and may be different for different kinds of products.
The case studies in the previous chapter illustrate some of the approaches used.
The design process starts with the designers working to develop a product that meets users’ requirements, but, as you have seen, understanding requirements tends to happen by a process of negotiation between designers and users. As designers understand users’ needs
better, their designs reflect this understanding. Similarly, as users see and experience design
ideas, they are able to give better feedback that enables the designers to improve their designs further. The process is cyclical, with evaluation facilitating understanding between
designers and users.
Evaluation is driven by questions about how well the design or particular aspects of it satisfy users’ needs and offer appropriate user experiences. Some of these questions provide high-level goals to guide the evaluation. For example, does this product excite users so that they will buy and use it? Others are much more specific. Can users find a particular menu item? Do they interpret a particular graphic as the designers intended and do they find it attractive? Practical constraints play a big role in shaping how evaluation is done: tight schedules, low budgets, or little access to users constrain what evaluators can do. There are ethical considerations too: medical records must be private and so are certain areas of people’s homes.
Experienced designers get to know what works and what doesn’t. As you have seen in
Chapter 12, there is a broad repertoire of evaluation methods that can be tailored for specific
circumstances. Knowing and having the confidence to adapt methods is essential. The wide
variety of mobile and ubiquitous systems coming onto the market challenges conventional
evaluation practices, which must be adapted to provide useful feedback. Therefore, when
planning evaluations, evaluators must consider the nature of each product, the kinds of users that will use it, and the contexts of use, as well as logistical issues, such as the budget,
the schedule, the skills and equipment required for the evaluation. Planning evaluation studies involves asking questions about the process and anticipating potential problems.
Within interaction design there are many books and websites that list different techniques and guidelines for conducting an evaluation, but there is very little overarching guidance for how to plan an evaluation. To help you, we propose the DECIDE framework, which provides a structure for planning evaluation studies.
The main aims of this chapter are to:
Discuss the conceptual, practical, and ethical issues involved in evaluation.
Introduce and explain the DECIDE framework.