EN ISO 4259-3:2020 PDF

Overview

EN ISO 4259-3:2020 - Petroleum and related products - Precision of measurement methods and results - Part 3: Monitoring and verification of published precision data in relation to methods of test (ISO 4259-3:2020) provides a standardized methodology for regularly monitoring whether the precision actually achieved by laboratories in proficiency testing (PT) matches the reproducibility precision published in a standard test method. It is targeted at petroleum and petroleum-related products where test items are presumed homogeneous, data distributions are approximately normal, and properties are stable during transport and storage.

Key topics and requirements

• Objective: Statistically compare standard deviation under reproducibility conditions achieved in PT programmes with the published reproducibility to verify representativeness.
• Scope limits: Applies to PTs run on standard test methods that have a published reproducibility (from ISO 4259‑1 studies), homogeneous samples and near‑normal data distributions.
• PTS provider requirements: Conformity with ISO/IEC 17043 for technical and management competence.
• Homogeneity & stability: Assessment of test item homogeneity and stability following guidance in ISO 13528 (Annex B).
• Data requirements:
  • Results must be numeric and single (no repeats per participant).
  • Minimum data size: at least 10 results (16 strongly recommended) and at least 6 uniquely different values after outlier rejection.
  • Outlier handling by generalized extreme studentized deviation (GESD) as in ISO 4259‑1 or equivalent.
  • Data distribution assessed for normality (e.g., Anderson–Darling or Shapiro–Wilk at 0.01 significance).
• Statistical methods:
  • PT standard deviation computed by the root-mean-square technique.
  • Main hypothesis testing via an F-test on the variance ratio to compare achieved vs published reproducibility.
  • Procedures for multiple comparisons over time to monitor trends.
  • Annex B gives guidance on using PT z-scores to monitor individual participant performance longitudinally.

Practical applications and users

Who benefits:

• Inter-laboratory comparison (PT) providers monitoring method performance across rounds.
• Analytical laboratories in the petroleum industry validating ongoing performance against published reproducibility.
• Quality managers and accreditation bodies assessing conformity with method precision claims.
• Standards developers and committee members reviewing whether published precision remains representative.
• Regulators and contract managers who rely on consistent, comparable test results for compliance and trade.

Practical uses:

• Regular verification that published reproducibility remains representative of routine laboratory performance.
• Identifying method drift or increased variability in practice.
• Supporting corrective actions, training, or method revision when PT precision consistently deviates from published values.
• Tracking individual laboratory performance using z‑score time series.

Related standards

• ISO 4259-1 - Determination of precision data in relation to methods of test
• ISO 13528:2015 - Statistical methods for use in proficiency testing by interlaboratory comparison
• ISO/IEC 17043 - Conformity assessment - General requirements for proficiency testing

Keywords: EN ISO 4259-3:2020, precision monitoring, proficiency testing, reproducibility, petroleum testing, F-test, z-score, interlaboratory comparison.