ISO 4259-5:2023

Overview

ISO 4259-5:2023 - "Petroleum and related products - Precision of measurement methods and results - Part 5" specifies a statistical methodology for assessing agreement between two different measurement methods that claim to measure the same quantitative property. The standard is intended for multi-sample–multi-lab studies (MSMLS), including interlaboratory studies (ILS) and proficiency testing programmes (PTP). Its primary output is the between-methods reproducibility (RXY) - the limiting difference between single results from two methods after any appropriate bias correction, expected to be exceeded with 5% probability under normal operation.

Key technical topics and requirements

• Applicability: Analytical methods measuring quantitative properties of petroleum and related products from MSMLS data (ILS, PTP).
• Data preparation: Computation of sample means and standard errors for each sample and method.
• Suitability checks: Tests for sufficient property variation, distributional checks, and correlation between methods (correlation coefficient ρ).
• Bias correction classes:
  • Class 0 - No bias correction.
  • Class 1a - Constant bias correction.
  • Class 1b - Proportional bias correction.
  • Class 2 - Both constant and proportional.
• Model selection and optimisation: Use of statistics such as sum of squared residuals (ΣSR) and total sum of squares (ΣST) to choose the appropriate bias-correction model.
• Validation steps: Confirming normal distribution of weighted residuals and assessment of sample-specific biases.
• Output: Calculation and reporting of between-methods reproducibility (RXY) and supporting statistics; guidance on required reporting elements.
• Annexes: Worked examples for ILS and PTP data to illustrate the procedure.

Practical applications and users

ISO 4259-5 is targeted at organizations and professionals involved in measurement quality and method evaluation in the petroleum sector, including:

• Testing laboratories and laboratory managers validating method comparability.
• Method developers and standards committees assessing interchangeability of methods.
• Proficiency testing providers designing PTPs and evaluating participants.
• Accreditation bodies and regulators reviewing method performance and measurement uncertainty.
• Quality assurance teams implementing statistical controls and bias corrections.

Practical uses include:

• Determining whether two analytical methods can be treated as equivalent for routine testing.
• Quantifying and applying linear bias corrections to improve agreement.
• Establishing acceptance limits (between-methods reproducibility) for compliance, reporting, and proficiency assessment.
• Supporting method validation, monitoring, and regulatory decision-making.

Related standards

• ISO 4259-1 - Determination of precision data (ILS design and analysis)
• ISO 4259-3 - Monitoring and verification of published precision data (PTP)
• ISO 4259-4 - Use of statistical control charts for single-lab validation

Keywords: ISO 4259-5, petroleum measurement methods, between-methods reproducibility, bias correction, interlaboratory study, proficiency testing, statistical assessment, analytical method agreement.