1.5 Designing for the user

　

The most satisfactory design will be one that is tailor made for the individual. Alas this personalized approach is far too expensive for all but those who can afford bespoke clothing or astronauts who must fit snugly into very personal aspects of their environment. For most designs, either of things that we use or spaces that we occupy, it is necessary to design for a population of users, called the target population. Some things that need to fit the user closely, like clothes, are designed in ranges of sizes. Some things that may not fit so well, like car seats and office furniture, can have some degree of adjustability. Other things that may not fit a lot of people well at all, like bus seats and toilets, are provided in one size only. Traditionally, the decisions about who to accommodate and whether to provide the user with choice or adjustability, are largely a matter of feasibility, function, economics, and what the market will stand. Whatever population is to be ‘fitted’, anthropometry provides the basic data upon which the design should be based. If only one user is involved then the relevant dimensions can be taken and the design fitted to the user in much the same interactive, iterative way that tailor made clothes are fitted. If a relatively small population of users is involved, like for astronauts, then it is possible to measure everyone in the population. Astronauts are usually male and have been selected on the basis of body dimensions so the variability to be found in such a population will be much less than in the general population. If a large population is to be fitted, like telephone users, then it is quite impossible to measure everyone and, either a sample may be taken or data may be obtained from existing sources.

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