4.4.5 Assigned values
4.4.5.1 The proficiency testing provider shall document the procedure for determining the assigned
values for the measurands or characteristics in a particular proficiency testing scheme. This procedure shall
take into account the metrological traceability and measurement uncertainty required to demonstrate that the
proficiency testing scheme is fit for its purpose.
NOTE Metrological traceability is not always possible or appropriate.
4.4.5.2 Proficiency testing schemes in the area of calibration shall have assigned values with
metrological traceability, including measurement uncertainty.
4.4.5.3 For proficiency testing schemes in areas other than calibration, the relevance, needs and
feasibility for metrological traceability and associated measurement uncertainty of the assigned value shall be
determined by taking into account specified requirements of participants or other interested parties, or by the
design of the proficiency testing scheme.
NOTE The required metrological traceability chain can differ depending on the type of proficiency test item, the
measurand or characteristic, and the availability of traceable calibrations and reference materials.
4.4.5.4 When a consensus value is used as the assigned value (see Annex B), the proficiency testing
provider shall document the reason for that selection and shall estimate the uncertainty of the assigned value
as described in the plan for the proficiency testing scheme.
4.4.5.5 The proficiency testing provider shall have a policy regarding the disclosure of assigned values.
The policy shall ensure that participants cannot gain advantage from early disclosure.
4.5 Choice of method or procedure
4.5.1 Participants shall normally be expected to use the test method, calibration or measurement procedure
of their choice, which should be consistent with their routine procedures. The proficiency testing provider may
instruct participants to use a specified method in accordance with the design of the proficiency testing scheme.
4.5.2 Where participants are permitted to use a method of their choice, the proficiency testing provider
shall:
a) have a policy and follow a procedure regarding comparison of results obtained by different test or
measurement methods;
b) be aware of which different test or measurement methods for any measurand are technically equivalent,
and take steps to assess participants' results using these methods accordingly.