Walter A Shewhart and His Contributions to Statistical Quality Control

Walter A Shewhart is a name highly revered amongst modern engineers as a man who married statistics, quality control, and process improvement in an era when quality control involved discarding defective items post-manufacture.

He is often regarded as the grandfather of total quality management and process improvement. Not only that, his concepts serve as a primer for quality engineers to this day.

Early Life, Work, and Contributions

Shewhart attended the University of Illinois at UrbanaChampaign before pursuing his doctorate in physics from the University of California, Berkeley in 1917. He worked for the Western Electric Company and was with the Inspection Engineering Department until 1925 when he joined the newly established Bell Telephone Laboratories.

Whilst at Bell Labs, Shewhart revolutionized the production process followed at the time. He leveraged schematic control charts of his creation to bring down the number of defective pieces being manufactured. This not only brought down costs for the company but also helped in building credibility among consumers.

Today, he is one of the most revered and well-respected personalities in the field of process improvement and quality. His contributions to process adjustments in manufacturing are still considered the founding stones for modern industry six sigma quality guidelines.

Shewhart’s contributions to Process Improvement Reducing variation

Shewhart is best known for his simple schematic control chart which changed the manufacturing industry forever. This chart outlined principles essential to modern process quality control. These are followed to this day with certain improvements as production processes became more complicated.

A key thing to remember in any process is that no two products will ever be the same. Reducing these variations to improve quality has always been one of the manufacturing industry’s greatest challenges. Dr. Shewhart’s acknowledgment of two classes of variation, namely special-cause’ and common-cause’ led him to improve his control chart mentioned above.

He proposed variables which would reduce common-cause’ variations. According to him, to distinguish between the two, every manufacturing process would need to be brought under statistical control. This and other principles of Shewhart helped pave the way for modern analysis of manufacturing processes.

Deming Wheel Cycle and Six Sigma

One of Shewhart’s other well-known accomplishments included a simple plan termed PDCA or plan-do-check-act, an iterative four-step management method for the continual improvement of processes. This is also known famously as the Deming Wheel cycle.

In six sigma programmes, the above-mentioned cycle is renamed as DMAIC or define-measure-analyze-improve-control. A guiding principle of the PDCA/DMAIC is the iterative nature of the processes. More the number of iterations a product is subjected to, the better the end output.

To illustrate and highlight his contribution to six sigma and the PDCA cycle, the latter needs to be looked at from the perspective of a company which isn’t experiencing profits.

The company would brainstorm ideas for improvement which is the plan’ phase of the cycle. Next, the company chooses an actionable course, then pursues it, which constitutes the “do” phase. The next phase check’ constitutes studies conducted to test the results of the actions taken prior. This phase also quantifies the efficacy of the prior phase and serves as the foundation stone for the next step. In the act phase, the company analyses the observed results. If the results are up to the mark, the process is set in stone until further improvements are needed. If they are not, this phase instructs the company to circle back to the original brainstorming pool to start the process over again and repeat the cycle until the company is pleased with the results.

This plan illustrates Shewhart’s brilliance and the thought process that the continuous evaluation of management procedures and the consideration of new ideas are vital in streamlining “common causes” and mitigating “special causes” in variation.

Conclusion

In conclusion, Shewhart is one of the most eminent contributors in Six Sigma and process improvement. His work and contributions help organizations identify unique attributes in their processes which influence customer experience and quality.

They will always be leveraged by organizations operating on the bleeding edge and wanting to re-define the way things are done.

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Harold French Dodge was born in Lowell in 1893 and was among the key architects of the field of SQC (Statistical Quality Control). Dodge completed his B.S. in electrical engineering from M.I.T. in 1916 and his master’s degree in physics from Columbia University in the year 1917. He worked at the Bell Laboratories quality assurance department from the year 1917 to 1958. His colleagues included Walter Shewhart, George Edwards, Harry Romig, R. L. Jones, Paul Olmstead, E.G.D. Paterson, and Mary N. Torrey. In 1958, after his retirement from the Bell Laboratories in 1958, he joined the Statistics Center of the Graduate School at Rutgers and became a professor of applied mathematical statistics until 1970. He was associated with NASA as an assurance consultant in 1961 and 1962 and with the Sandia Corp. from 1958 to 1967.

He is universally acclaimed for originating acceptance sampling plans for taking inspection operations on a scientific basis in terms of controllable risks. He also originated some other concepts such as skip-lot sampling plans, CSP type continuous sampling, acceptance sampling schemes, and chain sampling plans.

He was the chairman of the American Standards Association (ASA, now the American National Standards Institute) War Committee Z1, which prepared the Z1.1, Z1.2, and Zl.3 quality control standards. The American Society for Testing and Materials honored Harold Dodge’s contribution and named him its Marburg Lecturer in 1954 and an honorary member in 1968.  He was a fellow member of the American Statistical Association, the Institute of Mathematical Statistics, and the Royal Statistical Society. Dodge was the recipient of the prestigious Shewhart Medal (1949), Grant Award (1972), and was the fifth Honorary member (1965). He was also one of the Fellows and founding members of the Society. Several patents on telephone instruments and electrical stethoscopes are held by Dodge. He also authored a number of articles pertaining to the analysis of heart and lung sounds, in addition to his articles on quality control and sampling inspection in various technical publications.

Major Contributions to Quality Improvement

Sampling Inspection Tables: Dodge was the member of a small group that developed the Army Ordinance standard sampling table; the Dodge-Romig Sampling Inspection Tables, developed with Harry G. Romig in the early 1930s and published in 1940, are his most prominent and pioneering work. In more than 30 quality control training conferences for Army Ordinance, he was associated as an instructor. He also chaired the ASQ Standards Committee for many years and was chairman of the American Society for Testing and Materials (ASTM) Committee E-11 on statistical methods.

Acceptance Sampling: It is an important field of statistical quality control, originally applied during World War II by the U.S. military for the testing of bullets. If every bullet was tested in advance, no bullets would be left to ship and on the other hand, if none were tested, defects might occur in the battlefield, with disastrous results. Dodge proposed that a sample should be picked at random from the lot, and on the basis of information yielded by the sample, a decision can be made regarding the status of the lot. The acceptance or rejection of the lot was then decided. This process is known as acceptance sampling.

Differentiation Between Acceptance Quality Control and Acceptance Sampling: Harold Dodge pointed out in 1969 that acceptance quality control is not the same as acceptance sampling. The former can be implemented in the form of an acceptance control chart, the control limits for which are computed using the specification limits and the standard deviation being monitored. The latter, however, depends on specific sampling plans, which when implemented indicate the conditions for the acceptance or rejection of the immediate lot.

Conclusions

One of the aspects of quality assurance is related to inspection and decision making regarding quality products. Harold Dodge significantly contributed to the field of statistical quality control with the development of inspection tables, devising the concept of acceptance sampling, and clarifying the differences between acceptance sampling and quality control.

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Joseph Moses Juran (1904) was born in Romania. He demonstrated his quest for knowledge since an early age; in school, his mathematical and scientific proficiency was brilliant. He was the first member of his family to enroll in the University of Minnesota in 1912. In 1924, he earned a bachelor’s degree in electrical engineering from the University of Minnesota and joined Western Electric’s Hawthorne Works.

His first job was in the Complaint Department. In 1925, the Bell Labs proposed the training of Hawthorne Works personnel in its new statistical sampling and control chart techniques. Juran was also chosen to join the Inspection Statistical Department, a small group of engineers charged with the application and dissemination of Bell Labs’ innovations in statistical quality control. This highly visible position was the stepping stone in Juran’s ascent in the organization. The complexity of this enormous factory, with a labor base of 40,000 workers, presented Juran his first ever challenge in management.

In 1926, a new program was introduced by a team of quality control pioneers from the Bell Laboratories to Hawthorne Works. Designed to implement new tools and techniques, the project posed the requirement of a training program. Juran became one of the two engineers from a group of 20 engineers for the Inspection Statistical Department.

The end of World War II compelled Japan to change its focus to become an economic power rather than being a military power. The attention of the Japanese Union of Scientists and Engineers JUSE was drawn to the first edition of Juran’s Quality Control Handbook in 1951 and they invited him to Japan in 1952. He campaigned for quality and quality management throughout his life. Juran wrote several books on the concept of quality and its applications.

Contributions to Quality Management

Pareto principle: In 1941, Juran applied the Pareto principle to quality concerns in the organization: 20% of the causes are responsible for creating 80% of the problems. This is also popularly quoted as “the vital few and the trivial many.” In the later years, Juran used this quote to signal that the remaining 80% of the causes cannot be ignored.

Management theory: Juran is widely acknowledged for the addition of the human dimension to quality management. He advocated the training and education of managers. Juran proposed that human relations problems are supposed to be isolated and that the fundamental cause of quality issues was resistance to change. Juran’s concept of quality management can be extended outside the factory to encompass non-manufacturing processes and those that are service related.

The Juran trilogy: Juran was one of the first to point out the cost of poor quality. He illustrated this concept in “Juran trilogy,” a cross-functional management approach, constituted of three managerial processes: quality planning, quality control, and quality improvement. He pointed out that without change, there will be a constant waste. However, margins will be higher and the increased costs are recouped after the improvement.

Transfer of quality knowledge between East and West: He became aware of the concept of quality circles during his visit to Japan in 1966. He preached this concept with enthusiasm in his assignments in the West. He acted as a moderator between the U.S. and Japanese companies looking for mutual and professional introductions to each other.

Conclusions

Joseph M. Juran has many contributions in the field of quality management. His book, the Quality Control Handbook’ is a classic reference for quality engineers to date. He transformed the Japanese philosophy of quality management and worked hard in shaping their economy helping them to become industry leaders.

Dr. Juran was the first to embed the human aspect of quality management, known as Total Quality Management. The involvement of top management, the Pareto principle, identifying the need for widespread training in quality, propagating the new definition of quality as fitness for use, and the project-by-project approach towards quality improvement are the ideas and concepts for which Juran is best known, and they are still widely used today.

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Eugene Lodewick Grant is a name not much heard around the great halls of modern engineering, but he was a stalwart in the field. Amongst select circles, he is best known for a book he published back in 1930 about engineering economics and quality control. Some feel that Grant could not get proper recognition despite receiving awards like the Shewhart Medal.

Early Life, Work, and Contributions

Eugene Grant hailed from Chicago, which was slowly evolving into an industrial hub in the roaring 20s. He had served the Navy during World War I after earning his Bachelor of Science degree from the University of Wisconsin in 1917. Around 1920, he decided to join the faculty of the Civil Engineering Department at the University of Montana. Later during the year, the professor earned himself a master’s degree in economics.

He later joined Stanford’s Civil Engineering Department in 1930 where his teaching assignment led him to write the classic textbook on the principles of engineering economy. More books soon followed on varied topics like statistical quality control, the fundamental principles surrounding depreciation, and books across basic cost accounting. These tomes have gone a long way in silently influencing the field of modern engineering.

The professor headed the department until 1956 thereby taking up the role of heading the Committee on Industrial Engineering.

Grant’s contributions to Quality Control and Engineering

One of Eugene Grant’s best known contributions to the field of quality revolved around statistical quality control. His brilliance lay in the way he could perform thought experiments whilst keeping the practicalities in mind. His work and importance cannot be fully appreciated without first understanding the power of what they can achieve.

1. Statistical Quality Control: Any expert would say that this is the term used to describe sets of statistical tools to study quality. Even to an engineering apprentice, the quality of finished products holds the greatest importance, as that is the only way economics can be successfully married to engineering to create sustainable profit synergies across the board.

Until the early 20th-century, quality was limited to disposing of defective products post-production. This system proved to be not only impractical but cost heavy as well. To counter this, the powerful mathematical tools of statistics were employed which gave way to a completely new way quality was viewed in industry and engineering. Injecting various variables of a production process into statistical equations would give ways to prevent a defect before actual production. These could be then leveraged to redesign and optimize processes as well.

Among Grant’s practices, he believed that at least 20 observations would be needed over at least two to 10 working days of any process to make any useful conclusions. The equations related to standard deviation would be leveraged to create bell curves which would then be studied. These measurements would help in quantifying the probability of a defect occurring in a particular manufacturing process.

Professor Grant’s books on statistical quality control throw deep insights into this field and the huge potential statistics has on quality and its control in engineering.

2. Engineering Economics: It doesn’t require an expert to figure out that engineering and economics are two sides of the same coin. The challenge lies in its application wherein different factors of engineering and economics must be balanced to attain profitability of a product. Eugene Grant’s astuteness lay in this perfect confluence of the two fields where he could bring in methods to improve both profits and engineering processes.

There are various basic principles outlined before and improved upon by the late professor that revolve around simple but basic aspects of a manufacturing process. These would center around developing alternative solutions and focusing on the differences among them. His book on the subject, which was in its first publication in 1930 has since been translated into various languages across the world.

 Conclusion

In conclusion, even though the name Eugene Grant doesn’t ring an immediate bell, he has done more than his fair share for the advancement of statistics in quality control. Even after all these years, his achievements and insights on the engineering economy continue to influence new students of the subject and will continue to do so for a great many years.

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