Walter Andrew Shewhart (March 18, 1891 - March 11, 1967) was a physicist, engineer and statistician, sometimes known as the father of statistical quality control.
W. Edwards Deming said of him:
Born New Canton, Illinois to Anton and Esta Barney Shewhart, he attended the University of Illinois before being awarded his doctorate in physics from the University of California, Berkeley in 1917.
Following a brief spell as an academic, in 1918 Shewhart joined the Western Electric Company, a manufacturer of telephony hardware for the Bell Telephone Company. Bell Telephone’s engineers had been working to improve the reliability of their transmission systems. Because amplifiers and other equipment had to be buried underground, there was a business need to reduce the frequency of failures and repairs. Bell Telephone had already realised the importance of reducing variation in a manufacturing process. Moreover, they had realised that continual process-adjustment in reaction to non-conformance actually increased variation and degraded quality.
In 1924, Shewhart framed the problem in terms of assignable-cause and chance-cause variation (now refered to as special cause and common cause variation) and introduced the control chart as a tool for distinguishing between the two. Shewhart stressed that bringing a production process into a state of statistical control. Shewhart worked to advance the thinking at Bell Telephone Laboratories until his retirement in 1956, publishing a series of papers in the Bell System Technical Journal.
His work was summarised in his book Economic Control of Quality of Manufactured Product (1931).
Shewhart’s charts were adopted by the American Society for Testing and Materials (ASTM) in 1933 and advocated to improve production during World War II in American War Standards Z1.1-1941, Z1.2-1941 and Z1.3-1942.
From the late 1930s onwards, Shewhart's interests expanded to include science and statistical inference. The title of his second book Statistical Method from the Viewpoint of Quality Control (1939) asks the audacious question What can statistical practice, and science in general, learn from the experience of industrial quality control?
Shewhart's approach to statistics was radically different from that of many of his contemporaries. He possessed a strong operationalist outlook, largely absorbed from the writings of pragmatist philosopher C. I. Lewis, and this influenced his statistical practice. In particular, he had read Lewis's Mind and the World Order many times. Though he lectured in England in 1932 under the sponsorship of Karl Pearson his ideas attracted little enthusiasm within the English statistical tradition. The British Standards nominally based on his work, in fact, diverge on serious philosophical and methodological issues from his practice.
His more conventional work led him to formulate the statistical idea of tolerance intervals and to propose his rules for data presentation.
He died at Troy Hills, New Jersey in 1967.
In 1938 his work came to the attention of physicists W. Edwards Deming and Raymond T. Birge. The two had been deeply intrigued by the issue of measurement error in science and had published a landmark paper in Reviews of Modern Physics in 1934. On reading of Shewhart's insights, they wrote to the journal to wholly recast their approach in the terms that Shewhart advocated.
The encounter began a long collaboration between Shewhart and Deming that involved work on productivity during World War II and Deming's championing of Shewhart's ideas in Japan from 1950 onwards. Deming developed some of Shewhart's methodological proposals around scientific inference and named his synthesis the Shewhart cycle (also know as the PDSA cycle PDCA cycle and Deming Cycle).
During the 1990s, Shewhart's ideas was put to use by a third generation of industrial managers as they adopt the Six Sigma approach to management. Shewart's ideas form the basis for a significant portion of Six Sigma statistical methodology (though as often is the case when ideas are applied, Six Sigma efforts, often oversimplify and misapply some of the ideas).
In his obituary for the American Statistical Association, Deming wrote of Shewhart:
As a man, he was gentle, genteel, never ruffled, never off his dignity. He knew disappointment and frustration, through failure of many writers in mathematical statistics to understand his point of view.
He was founding editor of the Wiley Series in Mathematical Statistics, a role that he maintained for twenty years, always championing freedom of speech and confident to publish views at variance with his own.
His honors included: