ISO 9001 - Control Chart in Monitoring Variation

If you monitor quality or process control through laboratory analysis results you can use a control chart to check if variability is normal or if special causes are present. If special causes are present, it makes sense to investigate to discover and eliminate them. If only random causes are present, and performance is not adequate, the system must be modified.

Moreover, the use of control charts makes the analysis and evaluation of the results much more objective because it does not depend on opinions or states of mind, it follows clear rules of interpretation.

If your question is not about quality or process control, but about the quality of laboratory results I do not use control charts, but Repeatability and Reproducibility (R&R) studies.