scope:

This practice describes techniques for conducting intralaboratory and interlaboratory studies, analyzing the results of intralaboratory and interlaboratory studies and the formulation of appropriate precision statements for TAPPI test methods. The recommended techniques have the primary purpose of providing reliable information on the basis of which a broadly applicable precision statement can be made regarding the performance of a TAPPI test method.

A sound statistical design is required in the planning of an interlaboratory study to achieve this objective. Two situations are considered: (a) repeatability or comparison of test results within a laboratory (same material, operator, apparatus, environmental conditions, making tests in the shortest reasonable timeframe); and (b) reproducibility or comparison of test results among laboratories (same material, but different operator, apparatus and perhaps environmental conditions).

There are a multitude of intermediate measures of precision, e.g. same laboratory and operator using different instruments or different laboratories using a shared calibration standard etc., which are not covered in this standard. All of these sources of variation are lumped into the reproducibility value.