13.2 DECIDE: A framework to guide evaluation
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 ...