Dr. W. Edwards Deming

Leaders should have some understanding of variation, including appreciation of a stable system, [and] some understanding of special causes of variation and common causes.

Dr. W. Edwards Deming

A fault in the interpretation of observations, seen everywhere, is to suppose that every event (defect, mistake, accident) is attributable to someone (usually the one closest at hand), or is related to some special event. The fact is that most troubles with service and production lie in the system and not the people.