Six SigmaQuality

SPCStatistical Process Control

Using control charts to monitor a process and distinguish normal variation from special-cause signals requiring action.

Statistical Process Control (SPC) monitors a process over time using control charts to separate routine "common cause" variation from "special cause" variation that signals something has changed and needs investigation.

SPC prevents two costly errors: tampering (reacting to normal noise) and missing real shifts. It is the day-to-day quality discipline that sustains the gains of a Six Sigma project and feeds capability analysis.

Go Deeper
Statistical Process Control guide→Process Capability guide→
Related Terms
Control Chart
A time-series chart with statistical control limits used to distinguish normal variation from special-cause variation.
Process Capability
Indices (Cp, Cpk) that compare the spread and centering of a process to its specification limits.
Sigma Level
A measure of process capability expressed in standard deviations between the mean and the nearest spec limit.
Six Sigma
A data-driven methodology for reducing variation and defects to no more than 3.4 per million opportunities.
DMAIC
The five-phase data-driven improvement cycle at the heart of Six Sigma for improving existing processes.

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