ASTM E2554 for Estimating and Monitoring the Uncertainty of Test Results
ASTM E2554 Standard Practice for Estimating and Monitoring the Uncertainty of Test Results of a Test Method in a Single Laboratory Using a Control Sample Program
6. General Considerations
6.1 Materials to be Used:
6.1.1 This methodology requires a quantity of stable and homogeneous material which will serve as the source of control samples (sometimes called check samples). The material shall be similar in composition to the samples of material routinely analyzed by this test method in this laboratory. By stable it is assumed that the test results obtained from this material should be consistent over the time interval that this material will be used. By homogeneous it is assumed that samples taken from the material source will not have a significant variation in the characteristic measured by the test method.
6.1.2 For destructive testing of control sample materials, provision shall be made for depletion and replacement of the control sample material.
6.1.2.1 In some cases, the test method may be nondestructive and the same material may be reused indefinitely.
6.1.2.2 In other cases, the material may be used up, deteriorate, or otherwise gradually change.
6.1.3 The test method should describe the best practices for preparing and storing the control material and taking the control samples.
6.2 Test Conditions:
6.2.1 An uncertainty estimation program should be designed to include all known sources of variation, such as operators (analysts), equipment, reagents, and so forth, and these should be deliberately incorporated into the design of the program. In general, these sources of variation will be defined (including acceptable tolerances) by the test method.
6.2.2 In cases in which control over such variations is not possible or undefined, at least 30 to 50 sampling periods shall be evaluated to permit environmental and other factors to be incorporated in the overall estimate.
