Skip to main content

Statistical Process Control (SPC)

A method of using statistical techniques to monitor and control processes by tracking variation over time.

Definition and context

SPC uses statistical methods to monitor process variation and identify signals that need investigation. It supports process control but does not guarantee stability or product conformity.

Metrics like process capability indices summarize how well a process fits within specification limits.

Setting up SPC

Teams choose the right chart type: X-bar, R, p-chart, or c-chart: based on the data and sampling strategy.

They calculate control limits from historical data and update them when processes change materially.

Responding to signals

Rules such as the Western Electric criteria help teams spot unusual patterns: a sudden spike, a slow drift, or a run of points on one side of the average: that need investigation before defects reach the customer.

Follow the reaction plan when a signal occurs. Check affected production and avoid adjusting machines in response to ordinary random variation.

Where this term fits in the workflow

Statistical Process Control (SPC) is usually shown in the process control and risk.

Terms that help factories monitor variation, validate capability, and reduce risk before defects escape.

What is KaizenQ?

KaizenQ helps factory teams record inspection results, defect photos, and notes in one report shared with the office.

Learn more
KaizenQ inspection report preview

Key takeaways

  • SPC distinguishes normal variation from signals that need action.
  • Control limits and rules guide timely response.

Practical guides

Compare with related terms

Next terms to read