Standard deviation for proficiency assessment

{
  "id": "MLC-T-CHM-011287",
  "term": "Standard deviation for proficiency assessment",
  "field": "Chemistry",
  "definition": "A measure of dispersion used to evaluate participants' results in a proficiency testing scheme, serving as the denominator of the z-score, which is the difference between a result and the assigned value divided by σpt. It can be read as the standard deviation of a hypothetical population of laboratories performing as required, and is set from prior experience, a fitness-for-purpose criterion, a model, or the spread of the participants' own results. A z-score beyond 3 in magnitude is conventionally an action signal.",
  "subject": "Analytical Chemistry",
  "see_also": [
    "proficiency testing",
    "proficiency testing scheme"
  ],
  "references": [
    "PAC, 2021, 93, 997. 'Metrological and quality concepts in analytical chemistry (IUPAC Recommendations 2021)' on page 1041 (https://doi.org/10.1515/pac-2019-0819)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/standard-deviation-for-proficiency-assessment/"
}