Statistical Process Control (SPC)

Statistical Process Control (SPC) : 

This tool is made by combining three elements - Statistics, Process & Control as described below-

Statistical Process Control (SPC) is a statistical method to monitor the performance of a process, using Control Charts to keep the process in statistical control and to distinguish between common cause & Special cause of variations in a process.

Common Cause: A cause of variation in the process is due to chance, but is not assignable to any factor. It is the variation that is inherent in the process. The process under the influence of a common cause will always be stable and predictable.

Special Cause: It is also known as “Assignable cause”. The variation in a process that is not due to chance therefore can be identified and eliminated. A process under influence of a special cause will not be stable and predictable.

Method to perform SPC:-

Control charts are graphical tools to present and analyze process performance in SPC. They are used to detect special cause variation and to determine whether the process is in statistical control (stable).

Statistical process control can be used in different phases of Six Sigma projects: 

• To understand the stability of a process.

• To detect special cause variation in the process.

• To identify the statistical difference between the two phases.

• To eliminate or apply the unnatural change in the process.

• To improve the quality and productivity.