Laboratory & Inspection Practice
Measurement uncertainty basics for accredited labs
A practical guide to identifying uncertainty contributors and reporting results correctly.
Why this matters
Credible accreditation depends on consistent methods, clear decisions, and evidence that stands up to independent review. This publication translates essential expectations into practical steps so teams can prepare, communicate, and operate with confidence.
Key requirements and expectations
- Link technical competence to methods, equipment, and personnel.
- Demonstrate control of critical technical activities.
- Show traceability, uncertainty, and data integrity.
- Maintain records that prove repeatability and validity.
- Uncertainty must be evaluated for each accredited method.
- Budgets must be traceable and updated with changes.
- Reporting should align with stated decision rules.
Evidence and records to prepare
- Method validation or verification records and approvals.
- Calibration certificates and equipment maintenance logs.
- Training and authorization records for technical staff.
- Proficiency testing results and follow-up actions.
- Uncertainty budgets with calculation sheets.
Common pitfalls to avoid
- Using unvalidated methods or undocumented deviations.
- Incomplete measurement uncertainty or traceability chains.
- Missing training records for authorized signatories.
- Sampling or chain-of-custody steps not controlled.
- Using a generic uncertainty budget across methods.
Practical checklist
- Confirm methods are validated or verified for intended use.
- Maintain up-to-date equipment and calibration schedules.
- Document staff competence and authorization limits.
- Review PT and QA results before external assessment.
- Review uncertainty budgets after equipment changes.