Quick questions on Ergonomics and human factors: O-Level Design Studies

Anthropometrics is the study and measurement of the human body: dimensions such as height, reach, hand size, sitting height, and limb lengths. This data is the raw material of ergonomic design, because it tells the designer the sizes real human bodies come in. Using anthropometric data, a designer can size a product so that it physically fits its users, for example setting a seat height, a handle size, or the height of a shelf within comfortable reach.

A crucial idea is that people vary greatly in size, and almost no one is exactly "average". Designing only for the average person would leave smaller and larger people poorly served. Designers therefore use percentiles: a range, commonly from the 5th percentile (a small user) to the 95th percentile (a large user), so the design suits the great majority of people. For some features you design for the small end (a control must be within reach of a 5th-percentile user) and for others the large end (a doorway must clear a 95th-percentile user).

Human factors also include how people perceive, think and respond, not just their bodies. This cognitive side covers making controls intuitive, information clear, and interfaces easy to understand, and reducing mental effort and the chance of mistakes. A well-designed control panel, for example, is not only physically reachable but also clearly laid out so users press the right button. Ergonomics, in its full sense, fits the design to the whole person, body and mind.