One of the facts of design engineering is that systems have to be well integrated. For example, it is obvious that if the computer control of an automotive engine does not interface well with the mechanical systems, then it is a bad design. What is often neglected in engineering is the fact that almost every design produced ultimately interacts with the most unpredictable and most valuable system in all of creation, the human being. Human factors engineering addresses the proper design of the interface between machine and person. A slip occurs when the correct goal is formed, but an inappropriate action is taken.
Mistakes involve a processing error, which results in choosing the wrong goal.
Skill-based errors are most often slips or lapses, slips being errors of commission, and lapses being errors of omission. An example of an error-provocative display involves the airplane dial altimeter, which displays the altitude of the plane. These altimeters have 3 needles rotating on a single dial numbered 1 to 10. One needle reads 10,000's of feet, one reads 1,000's, and one reads 100's of feet. In 1949, a study showed that it took pilots over 7 seconds to decipher the altimeter.