statistical-process-control

Statistical process control (SPC) is a quality management methodology that applies statistical methods to monitor and control a process in real time. It distinguishes common-cause variation (inherent to the system) from special-cause variation (assignable to specific factors), enabling operators to intervene only when the process drifts outside statistically determined control limits. The core mechanism is the control chart — a time-ordered plot of a process metric against upper and lower control limits (typically ±3 standard deviations from the mean). SPC persists through documented procedures, trained personnel, calibrated measurement systems, and the institutional habit of data-driven decision-making. [formal: spc | substrate: behavior | horizon: hours | explicit: yes | epoch: 0.01]