X2.1.1.3 Proficiency Tests—Participation in proficiency test
programs is important for demonstrating how the laboratory’s results compare with other laboratories. Over a period of time,
laboratory bias can be demonstrated, if bias exists.
X2.1.1.4 ASTM Round Robins (Interlaboratory Tests)—
These programs are similar to proficiency test programs but are
limited to only a few laboratories and a few materials.
However, these programs do provide information on how well
the laboratory performs the test.