Why Do You Need an Interlaboratory Study Program?
Precision and Bias in ASTM Test Methods
All ASTM standard test methods must include a precision and bias statement, per Section A.21 of the Form and Style for ASTM Standards of the Form and Style for ASTM Standards. These statements strengthen the perceived quality of the standard test method. They also let users know that a test method has been laboratory tested.
The two measurements that serve to express precision in the evaluation of a standard test method are repeatability and reproducibility:
-
Repeatability - addresses variability between independent test results gathered from within a single laboratory (otherwise known as intralaboratory testing)
-
Reproducibility - addresses variability among single test results gathered from different laboratories (otherwise known as interlaboratory testing).
While Bias is defined as a systematic error that contributes to the difference between the mean of a large number of test results and an accepted reference value. When included in an ASTM test method, this statement describes the bias. It is important to remember that if an accepted reference value is not available, then the bias cannot be established. However, if the bias is unknown but the direction or bounds of the bias can be estimated, this information should be included in the bias statement.
Additional Information: Ruggedness Testing; Pilot Testing
We have created custom templates to assist you in drafting your Precision and Bias Statements:
Precision and Bias Template
Repeatability Precision Template