Walter A. Shewhart

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Walter A. Shewhart
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Walter A. Shewhart

Walter A. Shewhart was born in 1891, New Canton, IL, died in 1967, Troy Hills, NJ. He was an American statistician, physicist, and engineer. Studied physics at the University of Illinois and University of California. Walter A. Shewhart was a father of statistical quality control. He changed direction of industrial history by linking together statistics, engineering and economics. His greatest achievement was inventing the control chart, which was a formulation of a scientific basis for securing economic control.

William Edwards Deming and Joseph M. Juran worked with Shewhart and learned from him basics of statistical quality approach. Therefore, Shewhart, however less known that Deming and Juran, can be viewed as a father of contemporary quality movement.

Industrial quality

In 1918 joined the Western Electric Company - manufacturer of telephone hardware for Bell Telephone. They had been working on improving the reliability of their transmission systems to reduce the frequency of failures and repairs. Shewhart's first assignment was to improve the voice clarity of the carbon transmitters in the handsets. Later he used his statistical methods in a final installation of central station switching system, then to factory production.

In 1924 Shewhart uncovered the problem in terms of assignable-cause and chance-cause variation and developed the control chart, a tool for distinguishing between that two. The use of tolerance limits was short-sighted because he realized that they provided a method for judging the quality of product that had already been made. Walter A. Shewhart distinguished between common causes, assignable causes and the natural variability of any process, lapse in the process which are economically reasonable to seek out and eliminate. Shewhart allowed managers to focus on future production, by using statistical probability. He worked in Bell Telephone Labolatories from 1925 to 1956.


Shewhart published a series of papers in the Bell System Technical Journal. His book Economic Control of Quality of Manufactured Product was a summary of his earlier work. He also wrote Statistical method from the viewpoint of quality control in 1939 and A study of the accelerated motion of small drops through a viscous medium in 1917. The American Society for Testing Materials (ASTM) in 1933 adopt Shewhart's control chart.

  • Control charts - it is the basic and oldest tool for statistical process control. Control charts are used to control variability and its causes. They are in the form of sheets that are so designed that operator can easily indicate changes of analysed parameter.
  • Statistical process control - it is a set of techniques and statistical methods used to assess the stability of the process. The purpose of SPC is to prevent non-conformity by detecting and early signalling of interference in the process.
  • Shewhart cycle - The PDCA cycle is also known as Shewhart cycle or Deming wheel. They all refer to the same tool of continuous improvement.

Examples of Walter A. Shewhart achievements

  • Walter A. Shewhart was an American statistician and physicist who is widely considered to be the father of modern quality control. He is credited with developing the concept of statistical process control (SPC), a method of using statistical analysis to monitor and control a process. SPC is used to detect and prevent errors in processes, and Shewhart's work laid the foundations for the field of Six Sigma.
  • Shewhart is also remembered for his pioneering work in the field of reliability engineering, which is the study of how to design products and systems that are robust and reliable. Shewhart developed the concept of the bathtub curve, which is a graphical representation of the lifecycle of a product or system, and is used to predict how likely it is to fail over time.
  • Shewhart also developed the Shewhart cycle, which is an iterative process of plan-do-study-act (PDSA). This is a method of continuous improvement that is used to develop and refine processes and systems. The PDSA cycle is still used today to improve the effectiveness of processes and systems in many industries.

Advantages of Walter A. Shewhart approach

Walter A. Shewhart's work is considered to be the foundation of quality control, and his methods are still widely used today. His work has a range of advantages, including:

  • Increased efficiency: Shewhart's methods allow companies to identify and eliminate inefficiencies in their processes, improving the overall quality of their products and reducing costs.
  • Improved customer satisfaction: By improving the quality of their products, companies can better satisfy their customers and increase loyalty.
  • Reduced risk of errors: Through Shewhart's methods, companies can identify potential sources of errors and take corrective action before they occur. This reduces the risk of producing faulty products and reduces the costs associated with recalls and other corrective measures.
  • Increased innovation: By identifying areas for improvement, companies can make their processes more efficient, allowing them to focus more on innovation and growth.
  • Improved quality: Shewhart's methods allow companies to identify and eliminate sources of defects, leading to improved overall product quality.

Limitations of Walter A. Shewhart approach

Walter A. Shewhart was a pioneer in the field of statistical quality control and is widely credited with developing the concept of statistical process control. Despite his contributions to the field, there are some limitations to his approach. These limitations include:

  • His approach is focused on the control of processes and does not address the design of processes or products. This limits the applicability of his approach to situations where the process or product has already been designed.
  • Shewhart's approach is often seen as complex and difficult to implement, requiring specialized knowledge and resources.
  • His approach does not provide guidance on how to respond to data that indicate a process is out of control. This means that Shewhart's approach is limited in its ability to provide corrective action in a timely manner.
  • Shewhart's approach is focused on the use of statistical methods to identify and monitor process variation. This limits its ability to identify root causes of process variation, which is necessary for effective corrective action.

Other approaches related to Walter A. Shewhart

Walter A. Shewhart's approach to quality control was revolutionary in its time, and has since been the foundation of a number of related approaches. These include:

  • Total Quality Management (TQM), which focuses on organizational processes, and customer satisfaction, rather than on individual products.
  • Six Sigma, which uses a set of tools and techniques to improve the quality of products and services.
  • Lean Manufacturing, which focuses on reducing waste, streamlining processes, and increasing efficiency.

These approaches all owe their roots to the work of Walter A. Shewhart, who developed the original principles of quality control.