The term ‘proficiency testing’ is one that every accredited calibration laboratory is quite familiar with. In basic terms it refers to a method of evaluating how well a laboratory is doing a particular calibration with respect to its claimed measurement uncertainty and how it fares with other participants.
Accrediting agencies require their laboratories to participate in a number of proficiency tests each year so that all of the items on their scope of accreditation are covered over a specified period of time. If a laboratory fails to do these tests or their results when doing them are not up to speed it could mean that a particular item is withdrawn from their accredited scope or their measurement uncertainty claim is adjusted to suit. In severe cases accreditation for the laboratory in total may be withdrawn.