Statistical Process Control
Also known as: SPC
Definition
Statistical Process Control (SPC) is a quality management method that uses statistical techniques — primarily control charts — to monitor and detect changes in a manufacturing process in real time.
In depth
SPC distinguishes between common-cause variation (the inherent noise of a stable process) and special-cause variation (signals that something has changed). The core tool is the control chart, which plots a process metric over time against upper and lower control limits derived from the process's own historical variation.
SPC was developed by Walter Shewhart at Bell Labs in the 1920s and popularised by W. Edwards Deming after WWII. It is required by IATF 16949 and is one of the six automotive Quality Core Tools (along with APQP, FMEA, Control Plan, MSA, and PPAP).
In practice, SPC catches process drift before it produces defects. A control chart that signals an out-of-control point lets an operator stop and investigate before scrap accumulates.