Proficiency testing commonly known as PT is the evaluation of participant performance against pre-established criteria by means of interlaboratory comparisons

Organization, performance and evaluation of measurements or tests on the same or similar items by two or more laboratories in accordance with predetermined conditions

1. quantitative scheme — where the objective is to quantify one or more measurands of the proficiency test item.
2. qualitative scheme — where the objective is to identify or describe one or more characteristics of the proficiency test item.
3. sequential scheme — where one or more proficiency test items are distributed sequentially for testing or measurement and returned to
   the proficiency testing provider at intervals;
4. simultaneous scheme — where proficiency test items are distributed for concurrent testing or measurement within a defined time period;
5. single occasion exercise — where proficiency test items are provided on a single occasion;
6. continuous scheme — where proficiency test items are provided at regular intervals;
7. sampling — where samples are taken for subsequent analysis; and data transformation and interpretation — where sets of data or other information are furnished
   and the information is processed to provide an interpretation (or other outcome).

1. evaluation of the performance of laboratories for specific tests or measurements and monitoring laboratories’ continuing performance;
2. identification of problems in laboratories and initiation of actions for improvement which, for example, may be related to inadequate test or measurement procedures, effectiveness of staff training and supervision, or calibration of equipment;
3. establishment of the effectiveness and comparability of test or measurement methods;
4. provision of additional confidence to laboratory customers;
5. identification of interlaboratory differences;
6. education of participating laboratories based on the outcomes of such comparisons;
7. validation of uncertainty claims;

Value attributed to a particular property of a proficiency test item

Observation in a set of data that appears to be inconsistent with the remainder of that set.

Statistical method insensitive to small departures from underlying assumptions surrounding an underlying probabilistic model

Measure of dispersion used in the evaluation of results of proficiency testing, based on the available information

Property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.

Uncertainty of measurement.

Non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used.