SPC (Statistical Process Control)

SPC (Statistical Process Control) is a tool that uses statistical methods to monitor and control production processes. It aims to distinguish between normal and abnormal variation by analyzing process data, so that timely actions can be taken to keep the process stable and improve product quality. In foreign trade, SPC is often used in supplier quality management, especially when buyers require suppliers to provide process capability indices (such as Cpk, Ppk) or control charts (such as X-bar R charts). Use cases include: new supplier audits, first article confirmation before mass production, and quality monitoring for long-term supply. Note: SPC emphasizes prevention rather than post-inspection, and requires accurate and continuous data collection. Also, SPC is often confused with SQC (Statistical Quality Control); the former focuses on process monitoring, while the latter focuses on finished product inspection. In addition, SPC requires the process to be in a state of control; otherwise the data is meaningless. Unlike AQL (Acceptable Quality Level), SPC does not rely on sampling acceptance but analyzes process variation in real time. If SPC is stipulated in a foreign trade contract, the control chart type, sampling frequency, and exception handling procedure should be clearly specified.