An introduction to design engineering

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# 4.4 Using numbers to design

To move forward with the desk problem, you needed to know how many other people might be your height. You found a certain desk height acceptable and might reasonably assume this is a good size for everyone of the same height. But how might you find out how many other people are your height?

There are many sources of data on sizes, from the very general (such as people’s heights) to the exceptionally specific (such as NASA’s guide to the sizes of things in space). Two key sources where a range of human data and information can be found are the British Standards Institute (BSI) and the Health and Safety Executive (HSE). The data they provide about the size and shape of people is called anthropometric data, which consists mainly of physical characteristics and measurements. These data values are derived using statistical methods that allow generalisations to be made about human characteristics, which can be used to inform the design process.

Making use of these datasets and applying knowledge of how people interact physically with objects can be a complex process and is a discipline in its own right. Ergonomics is the study of physical aspects of the human body, such as size and mechanical performance, and how these can be applied to the real world. For example, in car design and manufacture, the design of a car interior has to take account of significant variation of human shape and size, and hence the range of adjustments that can be made to a car seat, seatbelt, steering wheel, etc. And that’s before you consider how these adjustments relate to one another, or are operated mechanically.

One useful way of presenting data, which is particularly useful for anthropometric data, is to create a histogram. Histograms offer a convenient way of presenting data to make it easier to read for a particular purpose. Instead of using a continuous spread of data, you divide it up into ‘buckets’ (often referred to as ‘bins’ or intervals) and sort items into them. For example, you could think of it as a way of sorting people into height ranges and then working out what proportion of people are in each range. Bar charts are similar, but can be used to represent categories of things that aren’t necessarily numerical.

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