Why do I have to take part in inter-laboratory tests?

ISO / IEC 17025:2005 "General requirements for the competence of testing and calibration laboratories" and accrediting agencies such as Cofrac encourage laboratories to take part in proficiency testing. Moreover, paragraph 5.9 of the standard 17025 requires laboratories to take measures to guarantee the quality of their test or calibration results. If your results are different from those of the other participants, then you should examine the impact of this difference on the results or the products delivered by your company since the last control operations.