Surveillance Testing and Round Robins

摘要

This paper discusses the correlation between internal and external process measurement controls for mass measurements to decide if laboratory measurements are in a state of statistical control. In the State Laboratories, two types of measurement control methods (internal and external) are used to determine if the standards are in control. Internal measurement control includes control charts and intercomparison of the standards where data are analyzed to verify that the standards are in a state of statistical control. The second method is external measurement control, which is performed with NIST-calibrated artifacts in round robins. The data obtained from these tests are evaluated and if the difference between the laboratory value and the NIST value is less than the combined uncertainty, the standard is considered in control. Cross checks between internal and external data provide a sound basis for evaluation of the measurement process and the standards used.