QEHSQuality
Statistical process controlSPC
A method of monitoring and controlling a process through statistical analysis of process outputs — detecting variation before it produces defects.
Statistical Process Control uses control charts (X-bar, R, p, c, u charts) to distinguish between common-cause variation (inherent to the process) and special-cause variation (assignable to a specific factor). When a process is "in control," all variation is common-cause and the process is predictable. SPC is a core tool in Six Sigma DMAIC, ISO 9001 quality management, and IATF 16949 automotive quality. Key concepts include control limits (typically ±3σ), process capability indices (Cp, Cpk), and the Western Electric rules for detecting out-of-control conditions.