Normal Distribution

Looking across a particular user population, we can measure a particular dimension or capability (such as height, for example).

Generally, we will find that the measured dimension forms a ‘normal distribution’.

A normal distribution is a type of probability distribution that is shaped like a bell curve. It is often used to describe the distribution of continuous variables, such as body size and strength, that tend to cluster around a central or average value and become increasingly rare as the values deviate from that average.

For example, if we were to plot the distribution of height among a group of people, we would likely see a bell-shaped curve with most people falling within a certain range of heights around the average, and fewer people falling outside of that range at the extreme ends of the distribution.

Similarly, if we were to plot the distribution of strength among a group of people, we would likely see a bell-shaped curve with most people falling within a certain range of strength around the average, and fewer people falling outside of that range at the extreme ends of the distribution. This is called the normal distribution. 

Normal distributions are important in HFE because they can help designers understand the range of body sizes and strengths that they need to accommodate in the design of workspaces and environments.