ISO 13528:2015 Statistical methods for use in proficiency testing by interlaboratory comparison
“This International standard provides detailed descriptions of statistical methods for proficiency testing providers to use to design proficiency testing schemes and to analyse the data obtained from those schemes. This standard provides recommendations on the interpretation of proficiency testing data by participants in such schemes and by accreditation bodies.
The procedures in this Standard can be applied to demonstrate that the measurement results obtained by laboratories, inspection bodies, and individuals meet specified criteria for acceptable performance.
This Standard is applicable to proficiency testing where the results reported are either quantitative measurements of qualitative observations on test items.”