The Relationship Between Quality Systems and the PDCA Cycle
Quality systems serve as systematic frameworks for continuously improving the quality of products and services and are widely implemented across various industries, from manufacturing to service sectors. The central concept for effectively operating these quality systems is the “PDCA cycle.” This article explains the utilization of the PDCA cycle in quality management systems in a manner that is accessible to beginners while maintaining professional rigor.
ISO 9001:2015 and the PDCA Cycle
ISO 9001:2015, published by the International Organization for Standardization (ISO), is the world’s most widely adopted standard for quality management systems (QMS). This standard defines quality management requirements applicable to organizations of any size or industry. As of January 2026, over one million certifications have been issued across 189 countries worldwide.
The introduction to ISO 9001:2015 explicitly mentions the importance of the process approach along with the application of the PDCA cycle. The entire structure of the standard itself is designed based on the PDCA cycle, and the application of this methodology to all processes is recommended.
Fundamentals of the PDCA Cycle
PDCA is an acronym representing four stages:
Plan: The stage of establishing objectives and processes to achieve them. This involves understanding the organization’s context, identifying stakeholder needs, and defining quality policies and objectives.
Do: The stage of implementing the planned processes. This includes securing necessary resources and deploying activities according to the plan.
Check: The stage of monitoring and measuring processes and products/services, and evaluating results against policies, objectives, and requirements.
Act: The stage of taking necessary actions to achieve planned results and realize continuous improvement.
This cycle was originated by Walter Shewhart, known as one of the fathers of quality control, and popularized by Dr. W. Edwards Deming. Dr. Deming initially used the term Plan-Do-Study-Act (PDSA), but it is now recognized worldwide as PDCA.
Structure of ISO 9001:2015 and the PDCA Cycle
ISO 9001:2015 has its entire requirement structure organized according to the PDCA cycle. Specifically, it corresponds as follows:
| PDCA Stage | Corresponding ISO 9001:2015 Clause | Main Content |
|---|---|---|
| Plan | Clause 4: Context of the organization<br>Clause 5: Leadership<br>Clause 6: Planning | • Understanding internal and external context<br>• Needs and expectations of interested parties<br>• Scope of QMS<br>• Quality policy and objectives<br>• Actions to address risks and opportunities |
| Do | Clause 7: Support<br>Clause 8: Operation | • Provision of necessary resources<br>• Competence, awareness, communication<br>• Determination of product/service requirements<br>• Design and development<br>• Control of external providers<br>• Provision of products and services |
| Check | Clause 9: Performance evaluation | • Monitoring, measurement, analysis, evaluation<br>• Customer satisfaction monitoring<br>• Internal audit<br>• Management review |
| Act | Clause 10: Improvement | • Response to nonconformities<br>• Corrective action<br>• Continual improvement |
Importance of the Process Approach
In ISO 9001:2015, the “process approach” is emphasized as one of the seven quality management principles, along with the PDCA cycle. The process approach is the concept that “desired results are achieved more efficiently when activities and resources are managed as processes.”
For an organization to function effectively, it must identify and manage numerous interrelated activities. All activities use resources (people, facilities, information, etc.) to transform process inputs into outputs (products/services). The output of one process often becomes the input of the next process.
In this way, processes do not function in isolation but form an integrated system that operates toward common objectives through mutual relationships and dependencies.
Major Process Groups in Quality Management Systems
Quality management systems consist of multiple process groups, each of which can apply the PDCA cycle. Major process groups include:
1. Management Processes
Management processes are the group of processes that define the direction of the entire organization and are responsible for strategic operation of the quality management system. Top management’s leadership and commitment are essential, determining the organization’s quality policy, objectives, and strategic direction.
Plan: Analysis of internal and external organizational context, understanding needs and expectations of interested parties, establishment of quality policy, setting quality objectives, planning actions to address risks and opportunities
Do: Communication of quality policy, assignment of roles, responsibilities, and authorities, leading and communicating direction throughout the organization
Check: Evaluation of QMS effectiveness through management review, review of objective achievement status, analysis of performance indicators
Act: Review of strategies and policies, direction of corrective actions, promotion of continual improvement
2. Resource Management Processes
Resource management processes are the group of processes that appropriately secure and manage resources such as “human resources, infrastructure, environment, knowledge, and financial resources” necessary for operating the quality management system.
Plan: Identification of necessary resources and allocation planning, definition of competence requirements
Do: Recruitment and placement of personnel, implementation of education and training, procurement and maintenance of facilities and equipment, establishment of work environment
Check: Monitoring resource utilization status, evaluation of competence, verification of facility adequacy
Act: Improvement of resource management, reallocation, implementation of additional education and training
Quality is supported by appropriate resources, and deficiencies in this process directly lead to quality degradation. ISO 9001:2015 also establishes clear requirements for personnel competence, awareness, and communication.
3. Product and Service Realization Processes
Product and service realization processes (operational processes) are the core group of processes for creating and delivering products and services that meet customer requirements.
Plan: Determination of product/service requirements, design and development planning, manufacturing/service provision process planning, external provider selection criteria
Do: Execution of design and development, provision of manufacturing/services, control of externally provided processes, products, and services
Check: Design and development review, verification, validation, process control, product/service inspection, release approval
Act: Response to nonconforming products/services, process improvement, response to customer feedback
By efficiently operating this PDCA cycle, it becomes possible to continuously provide products and services with high customer satisfaction.
4. Measurement, Analysis, and Improvement Processes
Measurement, analysis, and improvement processes (performance evaluation and improvement processes) are the group of processes that evaluate the effectiveness of the entire quality management system and promote continual improvement.
Plan: Planning of monitoring and measurement, planning of internal audits, setting improvement themes
Do: Collection of performance data, implementation of customer satisfaction surveys, execution of internal audits, conduct of management reviews
Check: Analysis and evaluation of data, identification of trends, review of audit findings, evaluation of customer satisfaction
Act: Response to nonconformities, implementation of corrective actions, deployment of preventive measures, standardization and sharing of best practices
This process includes internal audits, customer satisfaction surveys, complaint analysis, and data analysis. The spirit of continuous improvement (KAIZEN) is reflected here, forming the organization’s quality culture.
Risk-Based Thinking and the PDCA Cycle
ISO 9001:2015 has newly introduced “risk-based thinking,” which is integrated into all stages of the PDCA cycle. This is positioned as a replacement for the conventional concept of “preventive action.”
Risk-based thinking means systematically identifying and addressing risks (possibilities of undesirable effects) and opportunities (possibilities of desirable effects) while considering the organization’s context and stakeholder needs.
By applying risk-based thinking at each stage of the PDCA cycle, the following effects can be expected:
- Plan stage: Proactively identify potential risks and opportunities and reflect them in planning
- Do stage: Implement risk mitigation measures and opportunity exploitation strategies
- Check stage: Evaluate the effectiveness of risk management
- Act stage: Improve risk response and address new risks and opportunities
Integration of Process Groups and Overall Optimization
These process groups do not operate independently but mutually feedback while comprehensively enhancing the organization’s quality level.
For example, when new strategies or policies are introduced in management processes, the plans for resource management processes and product/service realization processes are revised accordingly. Insights gained from measurement, analysis, and improvement processes are reflected in the PDCA cycles of all other processes, leading to the next cycle.
Through this mutual integration, the quality management system becomes not merely a collection of procedures but a comprehensive system that describes the organization’s operations and provides useful information (such as data analysis).
Best Practices for Implementing the PDCA Cycle
To effectively operate the PDCA cycle, it is important to consider the following points:
Equal Focus: Many organizations tend to allocate significant time to the Plan and Do stages, but the Check and Act stages need equal emphasis. Balanced focus on all these stages is key to continuous improvement.
Clear Goal Setting: In the Plan stage, clearly define “what,” “how much,” “where,” “who,” and “when.”
Data-Driven Decision Making: In the Check stage, conduct evaluations based on objective data and information. Do not rely solely on intuition or experience.
Root Cause Analysis: In the Act stage, not only address surface issues but identify and eliminate root causes of problems.
Standardization and Horizontal Deployment: Standardize improvements whose effectiveness has been confirmed and deploy them throughout the organization.
Continuous Implementation: The PDCA cycle is not a one-time effort but demonstrates its effectiveness through continuous operation.
Developments in Modern Quality Management
As of 2026, quality management systems have undergone the following developments:
Advancement of Digitalization: The utilization of cloud-based quality management solutions enables real-time data collection and analysis, allowing organizations to operate the PDCA cycle more rapidly.
Integration with Other Management System Standards: ISO 9001 adopts a common High Level Structure with ISO 14001 (Environmental Management), ISO 45001 (Occupational Health and Safety Management), ISO 27001 (Information Security Management), and others, facilitating the integration of multiple management systems.
Strengthening Customer Centricity: Advances in digital technology enable faster and more detailed collection and analysis of customer feedback, directly contributing to improved customer satisfaction.
Conclusion
The PDCA cycle in quality management systems is a fundamental framework for systematically establishing and operating organizational quality management. ISO 9001:2015 has its entire standard structure designed based on the PDCA cycle, achieving effective quality management by combining the process approach with risk-based thinking.
It is important to correctly understand the roles of each process group within the organization, apply the PDCA cycle to each, and manage the interactions between processes. Additionally, focusing equally on all PDCA stages, making data-driven decisions, and continuously operating the cycle lead to enhanced organizational competitiveness, improved customer satisfaction, and sustainable growth.
When involved in implementing or operating quality management systems, understanding the principles of the PDCA cycle and integrating the process approach with risk-based thinking enables the construction of a quality management system that brings true value to the organization.
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