The , , and percentiles help designers accommodate different body sizes within a target population. Designers generally use the percentile for reach or minimum dimensions, the percentile for clearance, and the range between them for adjustable products.
Anthropometric data are measurements of human body dimensions, such as stature, hand width, or seated eye height. A percentile indicates the percentage of the sampled population whose measurement is equal to or below a stated value.
For example, a -percentile male stature means that of males in the relevant population are that height or shorter. It does not mean that one person is in the same percentile for every body measurement.
| Percentile | Meaning | Typical design use |
|---|---|---|
| Only of the population has a smaller measurement | Reach distances, control locations, and minimum operating forces | |
| The median measurement: half are smaller and half are larger | A reference value or compromise when adjustment is impossible | |
| have a smaller measurement; only are larger | Clearances, openings, headroom, legroom, and access spaces |
For a control panel, designing the maximum reach distance for a -percentile user allows most larger users to reach it as well. In contrast, a doorway based on a -percentile stature provides clearance for most users.
An adjustable office chair may span from the -percentile user to the -percentile user, accommodating approximately of the target population. The excluded extremes may require specialized designs.
A common misconception is that designing for the percentile fits most people. It fits the median measurement, but it may fit relatively few users well when several body dimensions are involved.
For A1.1 Ergonomics, identify the relevant anthropometric measurement and justify the chosen percentile. Link small-user reach to the percentile, large-user clearance to the , and inclusive adjustment to the -to- range.
