Internal quality control (IQC) of routine analysis can be applied in two different ways, statistical IQC and target value IQC. The correct interpretations of the respective control charts differ and are easily confused. This note examines statistical IQC in detail. It shows that its legitimate function is to ensure that variation in the run-to-run performance of the analytical procedure is inconsequential. Statistical IQC per se can say nothing about the uncertainty that can be attributed to the analytical results produced for the test samples. However, given an ‘in-control’ run, analysts can deduce that the uncertainty has not changed since the procedure was validated.

常规分析的内部质量控制（IQC）可以两种不同的方式应用，即统计IQC和目标值IQC。各个控制图的正确解释各不相同，并且很容易混淆。本说明详细研究了统计IQC。它表明，其合法功能是确保分析程序的每次运行性能之间的差异是无关紧要的。统计IQC本身不能说不确定性，该不确定性可以归因于测试样品产生的分析结果。但是，在“控制中”运行的情况下，分析人员可以推断出，自从验证过程以来，不确定性并未改变。