WALTER ANDREW SHEWHART: Father of Statistical Quality Control
BACKGROUND
Education
Walter Andrew Shewhart’s background was not out of the ordinary. He was born to Antonton and Esta Barney Shewhart on March 1891. He was Illinois-grown and received his bachelor and masters degrees from the University of Illinois. However, in 1914, when he married Edna Hart, the 23-year old moved to California, where three years later, he earned his doctoral degree in physics “while studying as a Whiting Fellow” from the University of California.
Work Experience
Between master’s and PhD degrees, he had teaching stints at the University of Illinois, University of California at Berkeley, and the now referred to as Wisconsin State University.
In 1918, however, he returned to Illinois to join Western Electric Company to work in its inspection engineering department. The Western Electric Company manufactured telephone hardware for Bell Telephone where engineers worked at improving the “reliability of their transmission systems”. Then, amplifiers and other equipment were buried underground, thus requiring reduction of the frequency of breakdowns and malfunctions.
Upon studying existent processes, Shewhart reached conclusions and suggested that every process shows degrees of variation because “no two things can be produced exactly alike”. He categorized these variations as chance cause variation and assignable cause variation. Chance cause variation is inherent in the process, random in nature, and uncontrollable. “Any process that operates with only chance cause variation is said to be in a state of statistical control. Once a process in in statistical control, adjustments can be made to minimize the random variation, which will improve the process. Assignable cause variation is a variation that is controlled by some outside influence of special cause, such as a change in material, operator, tool setting, tool wear or other phenomena. Any process that operates with assignable cause variation is said to be out of control. By using Shewhart’s control charts, outside influenced can be identified and controlled.” This principle birthed the modern scientific study of process control.
In 1925, Shewhart moved to the Bell Telephone Laboratories and advanced his theories and to include principles of statistics, engineering, and economics. In 1931, he published Economic Control of Quality of Manufactured Products.
In 1933, the American Society for Testing Materials (ASTM) adopted Shewhart’s charts and advocated to improve production during the World War II. He was made consultant of the US War Department, United Nations, and India. In the years that followed he lectured on quality control and applied statistics in India, London, and in graduate schools of the US Department of Agriculture.
Between 1941-1942, W. Edwards Deming made a “systematic critique of data-based management” based on Shewhart’s ideas. Deming championed Shewhart’s methods, which was later named Shewhart Cycle, when he worked as industrial consultant for the Japanese and later for the Americans from 1950 to 1990. Deming’s strategy gave rise to the “dramatic increase in Japanese productivity” for the period.
In the 1990s, his work was repackaged and incorporated in the Six Sigma Approach by “a third generation of industrial engineers and managers”.
Shewhart received many honors and awards that include: Holley Medal of the American Society of Mechanical Engineers, ASQ’s 1st Honorary Member, Founding Member and Fellow of the Institute of Mathematical Statistics, Fellow of the American Statistical Association, Fellow of the International Statistical Institute, Fellow of the Royal Society of Mechanical Engineers.
PUBLICATION/S
1. Economic Control of Quality of Manufactured Product (1931)
Presented in the book are the fundamental concepts and concepts of statistical control; ways of expressing quality of product (a section containing a discourse that has been described as a masterpiece on the meaning of quality); the basis for specification of quality control; sampling fluctuations in quality; allowable variability in quality (which contains the first fully developed use of control charts); and quality control in practice.
CONTRIBUTIONS
Shewhart fathered or even grandfathered total quality management. His ideas were developed and used as basis for other quality control practices by gurus of management specifically by Deming. In particular, he contributed to the field of management:
Statistical Process Control Methods. These methods are applicable to varied fields. “SPC is based on the idea that these attributes have two sources of variation: natural (also known as common) and assignable (also known as special) causes. If the observed variability of the attributes of a process is within the range of variability from natural causes, the process is said to be under statistical control. The practitioner of SPC tracks the variability of the process to be controlled. When that variability exceeds the range to be expected from natural causes, one then identifies and corrects assignable causes.” The key steps for implementing Statistical Process Control are:
o Identify defined processes
o Identify measurable attributes of the process
o Characterize natural variation of attributes
o Track process variation
o If the process is in control, continue to track
o If the process is not in control:
- Identify assignable cause
- Remove assignable cause
- Return to “Track process variation
Shewhart Cycle Learning and Improvement Cycle. Combining both management thinking and statistics, Shewhart developed this cycle with four steps: Plan, Do, Study, and Act. These four, he believed lead to total quality improvement.
REFERENCES
5. Omachonu, V.K. & Ross, J.E. (2004). Principles of total quality. USA: CRC Press.
6. Rose, K. (2005). Project quality management: Why, what, and how. USA: J. Ross Publishing, Inc.
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