Walter A Shewhart

Born: March 18, 1891

Died: March 11, 1967

Walter Shewhart is best known for:

Control Charts - Control Charts laid the foundation of Statistical Process Control (SPC) and modern quality improvement practices, including Six Sigma.

Assignable and Chance Cause of Variation

PDCA Cycle

A Brief Introduction:

Walter Andrew Shewhart was an American physicist engineer and statistician, sometimes known as the father of statistical quality control.

Most of Shewhart's professional career was spent as an engineer at Western Electric from 1918 to 1924, and at Bell Telephone Laboratories, where he served in several capacities as a member of the technical staff from 1925 until his retirement in 1956.

He also lectured on quality control and applied statistics at the University of London, Stevens Institute of Technology, the graduate school of the U.S. Department of Agriculture, and in India.


1917: Received doctorate in Physics from the University of California at Berkeley

1924: He introduced Control Charts as a tool to distinguish between the assignable and the random causes of variation.

1931: Published Economic Control of Quality of Manufactured Products.

Control Charts

Control charts are also known as Shewhart charts (after Walter A. Shewhart ).

Shewhart classified the causes of variation as "assignable cause" and "chance cause".

PDCA Cycle

The original founder of the PDCA cycle (Plan-Do-Check-Act) is Walter A. Shewhart.  Edwards Deming promoted the use of the PDCA cycle for process improvement and later changed it to the PDSA cycle (Plan-Do-Study-Act).

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History of Six Sigma | Quality Gurus - last week

[…] The concept of Six Sigma was developed in 1987 by Motorola. Six Sigma is basically a packaging of a lot of quality tools. These quality tools were developed much before 1987. One of the tools which form the basis of Six Sigma is the Control Chart. Control Charts were created way back in 1924 by quality guru Walter Shewhart. […]

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