One of the three cyclical quality assurance activities, quality control, is an umbrella of activities to certify a system is under statistical control.

These activities include quality control charts, proficiency testing, documenting, and archiving.

A quality control chart is a consecutive plot of one characteristic of the analysis that can act as a qualitative indicator.

The specific analysis characteristic is compared to the known characteristic value of the reference material. An inspection of the analysis conditions is required when the measured value falls outside the range of controlled limits for a selected standard deviation from the reference value.

Proficiency testing is the analysis of performance across multiple laboratories. Each lab's result is compared to the mean of results from all labs as the reference or against a certified reference material. The variations from different laboratories are characterized by the z score.