Good questions, in general the standard has an annex addressing repeatability and reliability, where the test was performed in several labs and shown to be repeatable and repoorducable.
How do you know the results you got were at all accurate or reproducible? ---We use equipment that is as accurate as required by the standard, and it is calibrated within the correct limits of accuracy and reproducibility.
If you ran the test over again, would you get similar results or wildly different?
---We get similar results.
How do you know you ran the tests correctly?
---You never really know that unless you are repeating each sample you test. The equipment is shown to be run repeatable at annual calibration.
That's my opinion, does anyone else have an opinion?