General Paper

Accreditation and Quality Assurance

, Volume 17, Issue 4, pp 389-393

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Determination of the standard deviation for proficiency assessment from past participant’s performances

  • Isabelle CôtéAffiliated withCentre de toxicologie du Québec (CTQ)/INSPQ Email author 
  • , Piotr RobouchAffiliated withEuropean Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM)
  • , Benjamin RobouchAffiliated withIstituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali di Frascati
  • , David BissonAffiliated withCentre de toxicologie du Québec (CTQ)/INSPQ
  • , Philippe GamacheAffiliated withCentre de toxicologie du Québec (CTQ)/INSPQ
  • , Alain LeBlancAffiliated withCentre de toxicologie du Québec (CTQ)/INSPQ
  • , Pierre DumasAffiliated withCentre de toxicologie du Québec (CTQ)/INSPQ
  • , Mikaël PedneaultAffiliated withCentre de toxicologie du Québec (CTQ)/INSPQ


The “uncertainty function” introduced by Thompson et al. estimates the reproducibility standard deviation as a function of concentration or mass fraction. This model was successfully applied to data derived from three proficiency testing schemes aiming at the quantification of cadmium, lead and mercury in blood and urine. This model allows the estimation of standard deviation for the performance assessment for proficiency testing rounds.


Horwitz equation Thompson-modified equation Uncertainty function Limit of detection Reproducibility Proficiency testing