Considering usability when designing - OCRErgonomics and anthropometrics

The relationship between anthropometrics and ergonomics needs to be understood so that they can be successfully utilised by designers.

Anthropometrics

Anthropometrics is the practice of taking measurements of the human body and provides categorised data that can be used by designers.

Anthropometrics help designers collect useful data, eg head circumferences when designing a safety helmet. In this example, as there is a large variation in size, the designer would need to build some adjustment into the safety helmet design.

Ergonomics

Ergonomics can incorporate the use of anthropometric data when designing products to improve the user experience. If a designer doesn’t use anthropometric data during the design process, it can lead to a poor user experience that causes discomfort, pain and potential injury. Ergonomics is a consideration that leads to a product being designed in a way to make it easy to use. Size, weight, shape, position of buttons and controls are all aspects that contribute to it being ergonomically designed. This is shown in practice in the image below of a woman sitting at her desk:

• table height makes it easy to reach the keyboard and mouse
• monitor height and angle of the monitor makes it easy for the user to see the screen reducing the strain on the neck, eyes and back
• seat height is adjustable so it can be set at a comfortable height for the user
• the user can sit at a comfortable distance from the desk so they do not have stretch to reach the keyboard and mouse
• position can be changed by adjusting the armrests and backrest - sitting in the correct position will reduce the strain on the body and increase the view angle of the screen

Designers should use anthropometric data to help make sure a product will be comfortable for the user. It is difficult to design a product that everyone will be able to use with comfort, so products are often designed for the majority of the population, considered to be between the 5th and 95th percentile:

• the 5^th percentile are the 5 per cent of people who are smaller in size
• the 50^th percentile are people of average size
• the 95^th percentile are 5 per cent of people who are larger in size

Below is an example of a set of anthropometric data for adults.

Male aged 19 to 60:

Female aged 19 to 60:

Example

A designer is designing an emergency stop button for a machine, which must be able to be pressed quickly and easily with the whole palm of the hand by the majority of the population. Using the table above, what is the minimum size the emergency stop button should be?

The handbreadth data from both tables provides the lowest 5^th and highest 95^th percentile data. This is:

• lowest = 71 mm (female)
• highest = 98 mm (male)

Using this information, the size of the button should have a minimum width of 98 mm.

As the button will be larger than the female 5^th percentile and equal to or larger than the male 95^th percentile it will be accessible for the majority of the population.