ASTM D6299 Evaluate Analytical Measurement System Performance
ASTM D6299 Standard Practice for Applying Statistical Quality Assurance Techniques to Evaluate Analytical Measurement System Performance
10. Validation of System Performance Estimates Using VA Samples
10.1 If the users decide to include VA sample testing as part of their QA program, then they should periodically evaluate the results obtained on the VA samples. The purpose of the evaluation is to establish whether the system performance estimates described in Section 9 are reasonably applicable to routinely tested samples.
10.2 VA sample test results should be evaluated independently through an internal or external audit system, or both. It is recommended that the internal audit team not be limited to the operators of the measurement system and their immediate supervisors.
10.3 Insofar as possible, analyze the results obtained on the VA samples separately and in the same manner as those from the routine QC and check standard testing program.
10.4 Using F or t tests, or both (see A1.8 and A1.6), statistically compare the system performance estimates obtained from the VA sample testing program to the measurement system accuracy and precision estimates from the QC sample testing program.
10.5 If the comparison reveals that the two estimates of the measurement system performance are not statistically equivalent, there is cause for concern that the actual performance of the measurement system may be significantly worse than estimated. Investigate thoroughly for the assignable cause(s) of this inconsistency, and eliminate it. Until the causes are identified and eliminated, the lab precision estimates of Section 9 should be considered suspect.
