The application of data from proficiency testing to laboratory accreditation according to ISO 17025

Kaj Heydorn

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Current methods of testing laboratories for their proficiency in reporting correct measurement results are liable to substantial errors of the 2nd kind. This means that laboratories with deflated uncertainties are accepted as proficient, even though their reported measurement results pave the way for erroneous conclusions. Only by using En numbers based on an accepted reference value with the lowest possible uncertainty can the risk of recognizing incorrect measurement results be kept at an acceptable level. Based on an actual set of PT-data for the concentration of Pb in water the paper compares proficiency test results obtained by methods using En numbers with methods based on z-scores.
Original languageEnglish
JournalAccreditation and Quality Assurance
Volume13
Issue number12
Pages (from-to)703-709
ISSN0949-1775
DOIs
Publication statusPublished - 2008

Keywords

  • En numbers
  • Fiddle factor
  • z-scores
  • Proficiency testing
  • Errors of the second kind
  • Type II error

Cite this

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The application of data from proficiency testing to laboratory accreditation according to ISO 17025. / Heydorn, Kaj.

In: Accreditation and Quality Assurance, Vol. 13, No. 12, 2008, p. 703-709.

Research output: Contribution to journalJournal articleResearchpeer-review

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PY - 2008

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AB - Current methods of testing laboratories for their proficiency in reporting correct measurement results are liable to substantial errors of the 2nd kind. This means that laboratories with deflated uncertainties are accepted as proficient, even though their reported measurement results pave the way for erroneous conclusions. Only by using En numbers based on an accepted reference value with the lowest possible uncertainty can the risk of recognizing incorrect measurement results be kept at an acceptable level. Based on an actual set of PT-data for the concentration of Pb in water the paper compares proficiency test results obtained by methods using En numbers with methods based on z-scores.

KW - En numbers

KW - Fiddle factor

KW - z-scores

KW - Proficiency testing

KW - Errors of the second kind

KW - Type II error

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JO - Accreditation and Quality Assurance

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