It was the Inspection Engineering Department of the Western Electric Company at Hawthorne that Shewhart joined in 1918. He worked there on statistical tools to examine when a corrective action must be applied to a process. His writings were on statistical control of industrial processes and applications to measurement processes in science. The control chart techniques which he developed have been widely adopted. His contributions are explained in more detail in :-
By the turn of the century, Western Electric had trained individuals as inspectors to assure specification and quality standards, in order to avoid sending bad products to the customer. In the 1920's, Western Electric's Dr Walter Shewhart took manufacturing quality to the next level - employing statistical techniques to control processes to minimize defective output. When Dr Shewhart joined the Inspection Engineering Department at Hawthorne in 1918, industrial quality was limited to inspecting finished products and removing defective items. That all changed in May 1924. Dr Shewhart's boss, George Edwards, recalled:The Bell Telephone Laboratories were founded in 1925 and Shewhart moved to them when the Laboratories opened and worked there until his retirement in 1956. He expanded his interests to a broader use of statistics over this period. During this period he published many articles papers in the Bell System Technical Journal. In addition, he published Random sampling in the American Mathematical Monthly in 1931. In 1939 he published the important book Statistical Method from the Viewpoint of Quality Control. It is interesting to read the publisher's description of the book:-
"Dr Shewhart prepared a little memorandum only about a page in length. About a third of that page was given over to a simple diagram which we would all recognize today as a schematic control chart. That diagram, and the short text which preceded and followed it, set forth all of the essential principles and considerations which are involved in what we know today as process quality control."
Mr Edwards had observed the birth of the modem scientific study of process control. That same year, Dr Shewhart created the first statistical control charts of manufacturing processes, which involved statistical sampling procedures. Shewhart published his findings in a 1931 book, Economic Control of Quality of Manufactured Product.
The application of statistical methods in mass production makes possible the most efficient use of raw materials and manufacturing processes, economical production, and the highest standards of quality for manufactured goods. In this classic volume, based on a series of ground-breaking lectures given to the Graduate School of the Department of Agriculture in 1938, Dr Shewhart illuminates the fundamental principles and techniques basic to the efficient use of statistical method in attaining statistical control, establishing tolerance limits, presenting data, and specifying accuracy and precision.In this book Shewhart asks:-
In the first chapter, devoted to statistical control, the author broadly defines the three steps in quality control: specification, production and inspection; he then outlines the historical background of quality control. This is followed by a rigorous discussion of the physical and mathematical states of statistical control, statistical control as an operation, the significance of statistical control and the future of statistics in mass production.
Chapter II offers a thought-provoking treatment of the problem of establishing limits of variability, including the meaning of tolerance limits, establishing tolerance limits in the simplest cases and in practical cases, and standard methods of measuring. Chapter III explores the presentation of measurements of physical properties and constants. Among the topics considered are measurements presented as original data, characteristics of original data, summarizing original data (both by symmetric functions and by Chebyshev's theorem), measurement presented as meaningful predictions, and measurement presented as knowledge.
Finally, Dr Shewhart deals with the problem of specifying accuracy and precision - the meaning of accuracy and precision, operational meaning, verifiable procedures, minimum quantity of evidence needed for forming a judgment and more.
What can statistical practice, and science in general, learn from the experience of industrial quality control?He wrote in this book:-
The definition of random in terms of a physical operation is notoriously without effect on the mathematical operations of statistical theory because so far as these mathematical operations are concerned random is purely and simply an undefined term. The formal and abstract mathematical theory has an independent and sometimes lonely existence of its own. But when an undefined mathematical term such as random is given a definite operational meaning in physical terms, it takes on empirical and practical significance. Every mathematical theorem involving this mathematically undefined concept can then be given the following predictive form: If you do so and so, then such and such will happen.Although working in industry for the whole of his career, Shewhart kept links with academic institutions being a lecturer in applied statistics at the Stevens Institute of Technology in Holboken in 1930, lecturing at the University of London in 1932 and at the United States Agricultural Graduate School in 1938. He was an honorary professor at Rutgers University in 1954 and a member of the advisory committee of the Princeton mathematics department during 1941-48. During 1944-46 he served on the National Research Council and for over 20 years he served as editor of the Mathematical Statistics Series of John Wiley and Sons.
Shewhart received many honours for his important contributions. He was a founder of the Institute of Mathematical Statistics, being elected a fellow and serving a term as vice-president in 1936 and president from 1936 to 1944. He was also a founder of the American Society for Quality Control. The Society made him their first honorary member in 1947 and also made him the first to receive their Shewhart Medal. The citation reads:-
The act of awarding the medal focuses the spotlight of public attention on the recipient, revealing in clear light the qualities that have won for him the esteem of his peers. What are the qualities that lead us to so honour a man as to give him a medal? First of all, he must have intellectual ability, enabling him to clear away a little of the dark cloud of ignorance that always surrounds us. Second, he must have the generosity of spirit that leads him to so express and restate his pioneering ideas that other members of his profession may benefit from them. And finally, he must have that warmth of human feeling that marks the true educator, endearing him to his students or disciples, even those who learn from him only remotely. All of these qualities are eminently personified in Dr Walter Shewhart.He was elected to a fellowship of the American Statistical Association, of the International Statistical Institute, and of the Royal Statistical Society. He was also elected to the American Association for the Advancement of Science (serving on the council during 1942-49), the Econometric Society, and the New York Academy of Science. He served a term as president of the American Statistical Association in 1945, and was awarded the Holley medal of the American Society of Mechanical Engineers in 1954. The Indian Statistical Institute in Calcutta awarded him an honorary doctorate.
Article by: J J O'Connor and E F Robertson