SPC | What is Statistical Process Control? | Methodology
During the 1920s, Walter A. Shewhart discovered a way to distinguish between common and special causes of variation in a process. This lead to an invention of the widely known method as statistical process control (SPC). He pioneered the use of statistical techniques for monitoring and controlling quality. Bell Labs wanted to economically monitor and control the variation in the quality of components and finished products. He recognized that inspecting and rejecting or reworking product was not the most economical way to produce a high-quality product. He demonstrated that monitoring and controlling variation throughout production was the more efficient and economical way.
Shewhart developed a visual tool for monitoring process variation, which came to be known as the control chart or the Shewhart control chart and the concept of a state of statistical control in 1924 at Bell Laboratories.
He has defined chance and assignable causes as the two sources of quality variation. A process that is operating with the only chance cause of variation is said to be in statistical control. A process that is operating with the assignable cause of variation is said to be out of control. The underlying concept of the Shewhart chart is to construct its limits based on variation allowable as it is in – control state and monitor the quality of the product produced.
Bell Labs was widely recognized as the ‘international standard for quality’ by the 1930s, due to the large applications of Shewhart’s techniques in the field of telecommunications. During this period, many initiatives were done by conducting extraordinary research in statistical methods to control and improve process variation. This leads to improve product quality in a great way.
His work was summarized in his books titled “Economic Control of Quality of Manufactured Product” (1931) and “Statistical Method from the Viewpoint of Quality Control” (1939).
Image – Referred from leansixsigmadefinition.com
