They are not caused by the organization (training, management, motivation, information, tools); for example, not by an incorrect Work-Process-Standard.
They can be used to improve things more locally, at the Level of the individual engineer. For example, by learning that they misinterpreted a Work-Process-Standard, motivating, teaching or instructing the individual.
Dr. Walter Shewhart (Deming and Juran”s teacher of SPC) called these “Chance-Causes. The main point is that Special-Causes may be treated by the individual worker, if they are given information and power, while Common-Causes must be treated by management. W. Edward Deming”s term (“special”) is the preferred term in this book.
This Concept entered by Diane O'Brien.