An airplane manufacturer designs a control panel covered with dials and lights. In addition to checking the panel in a factory setting, the manufacturer must also be sure the panel works for the people who will be using it. For example, will pilots notice when a warning light is on?
Human factors engineers study how sensation and perception interact with machines and equipment. A pilot might be tested to see how dim a light she can detect 50% of the time (absolute threshold). A pilot might also be tested to determine how different the intensity of two lights would have to be for her to detect a change 50% of the time (difference threshold). Using information gathered by a human factors engineer, the manufacturer could accurately set the brightness of lights on the panel.