Overview
ISO 14253-1:2017 - part of the Geometrical Product Specifications (GPS) suite - defines decision rules for verifying conformity or nonconformity of workpiece characteristics and measuring equipment by measurement. The standard requires that measurement uncertainty be taken into account when assessing whether a measured value meets a specification (tolerance or maximum permissible error). It applies to specifications given as quantity values and is primarily intended for standards prepared by ISO/TC 213.
Key topics and technical requirements
- Decision rules for conformity assessment: Defines how to decide acceptance or rejection when measured values lie close to specification limits, using probability-based rules rather than a simple pass/fail.
- Measurement uncertainty integration: Requires considering estimated measurement uncertainty and the associated probability density function (PDF) when verifying conformity or nonconformity.
- Acceptance zone / Rejection zone / Uncertainty zone:
- Acceptance zone - intervals where conformity can be verified with an agreed conformance probability.
- Rejection zone - intervals where nonconformity can be verified.
- Uncertainty zone - intervals near specification limits where neither conformity nor nonconformity can be established due to uncertainty.
- Probability limits and guard bands:
- The standard sets a default conformance probability of 95%, replacing the earlier default coverage factor approach (k = 2), to keep the risk of false acceptance constant.
- Guard bands are defined around specification limits to separate acceptance, rejection and uncertainty zones.
- Scope of application:
- Applies to workpiece characteristics, population specifications, and metrological characteristics of measuring equipment (maximum permissible errors).
- Only valid for characteristics expressed as quantity values.
- Supplier/customer roles: Provides guidance on applying decision rules in supplier–customer contexts, including when parties should agree on decision criteria in advance.
- Related terminology and normative references: Uses concepts from ISO/IEC Guide 98 series (GUM) and ISO vocabularies (ISO 3534-2, ISO 9000).
Practical applications and users
Who uses ISO 14253-1:2017:
- Quality engineers and metrologists who perform inspection by measurement
- Calibration laboratories and inspection services applying conformity assessment
- Suppliers and customers negotiating acceptance criteria and inspection plans
- Standards writers and auditors implementing GPS-compliant verification procedures
Practical benefits:
- Reduces disagreement on near-limit measurements by formalizing decision rules
- Improves traceability and consistency in inspection results by explicitly accounting for measurement uncertainty
- Supports risk-aware acceptance sampling and calibration decisions
Related standards
- ISO 14638 (GPS matrix model)
- ISO/IEC Guide 98-3 (GUM) and Guide 98-4 (uncertainty in conformity assessment)
- ISO 3534-2, ISO 9000, ISO/IEC Guide 99 (VIM)
- ISO 8015 (fundamental GPS rules)
- ISO 18391 (population specification details)
Keywords: ISO 14253-1:2017, geometrical product specifications, GPS, decision rules, measurement uncertainty, conformity assessment, acceptance zone, uncertainty zone, guard band, inspection by measurement.