Overview
ISO 7870-2:2023 - “Control charts - Part 2: Shewhart control charts” is an international standard that provides a clear, practical guide to using Shewhart control charts for Statistical Process Control (SPC). The document focuses exclusively on the Shewhart approach to monitoring process stability and identifying assignable causes of variation. It also briefly introduces compatible topics such as warning limits, trend/pattern analysis, and basic process capability considerations.
Keywords: ISO 7870-2, Shewhart control charts, control charts, statistical process control (SPC), process capability, industrial quality control
Key Topics
- Core concepts: Definitions of Shewhart control charts, control limits, action limits, warning limits, Type I and Type II errors, and what it means for a process to be in statistical control.
- Phases of control: Guidance on Phase 1 (initial analysis and set-up) and Phase 2 (ongoing monitoring).
- Chart types covered: Variables charts (X̄ & R, X̄ & s, individuals X and moving ranges R, median charts) and attribute charts (e.g., p charts for fraction nonconforming).
- Control procedure: Steps for data collection, chart construction, examining and homogenizing variation charts, and interpreting X and variation charts.
- Pattern tests and assignable causes: Recognition of unnatural patterns, tests for assignable causes, and practical notices on investigating out-of-control signals.
- Process capability & improvement: Introductory treatment of linking control to capability and improvement actions.
- Cautions & limitations: Notes on correlated data, alternative rule sets to the three-sigma rule, and contexts where other chart types might be more appropriate.
Applications
ISO 7870-2:2023 is practical for organizations and professionals who need standardized, reliable methods for process monitoring and improvement:
- Quality engineers and statisticians implementing SPC on production lines.
- Process engineers and manufacturing managers in discrete and continuous industries (automotive, electronics, chemical, pharmaceutical, food).
- Quality assurance teams and auditors assessing control systems and compliance with quality management systems.
- Suppliers and contract manufacturers establishing control plans and supplier quality monitoring.
Typical uses include real-time process monitoring, early detection of special causes, reducing waste through prevention (rather than end‑of‑line inspection), and forming the statistical basis for process improvement projects.
Related Standards (if applicable)
- Part of the ISO 7870 series - consult the ISO website for other parts covering additional chart types and broader SPC guidance.
- Prepared by ISO/TC 69 (Applications of statistical methods) - aligns with general SPC best practices used in ISO-based quality management systems.
For implementation, users should combine ISO 7870-2 guidance with organization-specific procedures, measurement systems analyses, and process capability studies.
