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The PeopleSize dataset has been produced to meet the needs of designers, on the pragmatic basis put forward by Pheasant (ref 57).
The needs of designers are for data that are:
- Likely to include all dimensions needed to size the design in hand
- Of the desired nationalities
- Of the appropriate age range for the product
- Recent enough to apply to current populations
- Free of large errors caused by small samples or lack of opportunity for validation against comparable datasets
Published data from individual surveys are necessarily characterised by smaller sample sizes, one population, and a limited number of dimensions. Many datasets are now more than a decade old.
Recognising that if data are not available then designers are forced to make their own, possibly inexpert, estimates, the procedures were developed to create a large up-to-date and validated dataset using a formal estimation method.
Although estimation is sometimes thought to be approximation, it often improves accuracy by revealing data errors (which are very common) and showing up inconsistencies. It is in any case fundamentally impossible to avoid estimation: it hardly ever happens that a user population is really the same as a sampled population, except for private data. It is also unlikely that one survey will measure all the dimensions needed for a series of designs.
See also: Estimation Methods (next Chapter)
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