This document covers statistical methodology for assessing the expected agreement between two test methods that purport to measure the same property of a material, and deciding if a simple linear bias correction can further improve the expected agreement.
This methodology is intended for test methods which measure quantitative (numerical) properties of petroleum or petroleum products.
It is intended for use with results collected from an inter-laboratory study meeting the requirement of ISO 4259-1 or equivalent (e.g. ASTM D6300). The inter-laboratory study must be conducted on at least ten materials that span the intersecting scopes of the test methods and results must be obtained from at least ten laboratories using each method.
The statistical methodology outlined in this practice is also applicable for assessing the expected agreement between any two test methods that purport to measure the same property of a material, provided the results are obtained on the same comparison sample set, the standard error associated with each test result is known, and the sample set design meets the requirements of this practice, in particular that the statistical degree of freedom associated with all standard errors are 30 or greater.