Shewhart, a statistician at Bell Telephone Laboratories, New York, developed techniques for bringing industrial processes into statistical control. His gift was to recognise when to act and when to leave a process alone. He taught that all processes show variation but that it is important to distinguish common cause variation from special (or assignable) causes.
To Shewhart goes the credit for much of the early work on process control which was to be a major influence over the work of W. Edwards Deming – including the Shewhart Cycle – Plan – Do – Check – Act, which later became better known as the Deming Cycle.