Walter A Shewhart and His Contributions to Statistical Quality Control

Walter A Shewhart and His Contributions to Statistical Quality Control

By Discovery Lean Six Sigma

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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 Urbana–Champaign 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.


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.

The post Walter A Shewhart and His Contributions to Statistical Quality Control appeared first on Shmula.

By: Shmula Contributor
Posted: February 28, 2019, 7:55 am

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