Interlaboratory evaluation of test methods to determine TAPPI repeatability and reproducibility

This practice describes techniques for conducting and analyzing the results of intralaboratory and interlaboratory studies. The steps described here will result in a good statistical design that provides sound data for formulating a broadly applicable precision statement regarding the performance of a TAPPI test method.

Two values are considered: (a) repeatability, which is defined as comparison of test results within a laboratory (same material, operator, apparatus, environmental conditions, making tests in the shortest reasonable timeframe); and (b) reproducibility, which is defined as comparison of test results among laboratories (same material, but different operator, apparatus and perhaps environmental conditions).

In the data chain leading to test results there are many possible sources of variation, and one can conduct studies to isolate these other sources, e.g. same laboratory and operator using different instruments or different laboratories using a shared calibration standard etc. For the purposes of TAPPI test methods, all of these sources of variation are to be captured in a reproducibility value.