A process can be defined as any procedure that requires repeatable actions. Processes can be as common as getting dressed in the morning, time to or from work, time to make a pot of coffee. Process variation in manufacturing may include differences in  part dimensions, texture, alloy composition, or even taste.

Statistical Process Control (SPC) is one of the most powerful tools that manufacturers have to ensure that they are making repeatable parts and assemblies. Statistical Process Control was developed in the the 1920 by Dr. Walter A. Shewhart at Bell Laboratories. It was then spread worldwide by his two students, Dr W. Edwards Deming and Joseph M. Juran.

SPC can be used to reduce variation in a process and to center that process. 

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