Introduction: Problem-Solving Beginning with “5 Whys Analysis”
In various industries such as manufacturing, software development, healthcare, and service sectors, the occurrence of “nonconformities” and “problems” is inevitable. When these arise, there is a tendency to rely on immediate solutions. However, to achieve true recurrence prevention and sustainable improvement, it is essential to accurately identify and address the “Root Cause” rather than superficial causes. This article provides an accessible yet professionally comprehensive explanation of root cause identification methods suitable for beginners while maintaining technical rigor.
The Difference Between Superficial Causes and Root Causes
When nonconformities or problems occur, people often focus on “visible causes” such as “operational errors,” “failure to confirm procedures,” or “defective parts.” While these superficial causes directly trigger the phenomenon, addressing them alone carries a high risk of similar nonconformities recurring over time.
In contrast, a root cause is “a more fundamental underlying factor” that explains why the superficial cause itself occurred. For example, behind an “operational error,” there often lie deeper structural issues such as “manuals not suited to actual workplace conditions,” “insufficient training,” or “inadequate workspace preventing adherence to proper procedures.”
The Position of Root Cause Analysis in ISO Standards
ISO 9001:2015 Clause 10.2, “Nonconformity and corrective action,” establishes a systematic approach for organizations to address nonconformities. This clause requires organizations to:
When a nonconformity occurs, the organization must respond to it and, where applicable, take action to control and correct it and deal with its consequences. Additionally, the organization must evaluate the need for action to eliminate the causes of the nonconformity to prevent recurrence or occurrence elsewhere. This evaluation includes reviewing and analyzing the nonconformity, determining its causes, and assessing whether similar nonconformities exist or could potentially occur.
Corrective actions must be appropriate to the effects of the nonconformities encountered. This means that while minor issues may be adequately addressed with a simple 5 Whys analysis, significant problems involving safety impacts or regulatory compliance violations require more comprehensive approaches, including detailed root cause analysis by cross-functional teams, utilization of fishbone diagrams, and potentially the deployment of Six Sigma projects.
Other ISO standards adopting the Annex SL structure, such as ISO 14001 (Environmental Management) and ISO 45001 (Occupational Health and Safety Management), similarly require root cause analysis in Clause 10.1 or 10.2. This establishes root cause analysis as a widely recognized international best practice.
Fundamental Methods for Identifying Root Causes
1. 5 Whys Analysis
The simplest and most effective method is the “5 Whys Analysis.” By repeatedly asking “Why did this occur?” about a nonconformity or phenomenon, one can progress from superficial causes to root causes. While it is generally said that asking “why” approximately five times brings one closer to the essence, the number is merely a guideline, and there is no need to adhere strictly to it if sufficient depth has been achieved. In some cases, the root cause may be reached in three iterations, while in others, seven or more may be necessary. The key is to continue asking until the true root cause is identified.
This method originates from the Toyota Production System and is also utilized in the Analyze phase of the Six Sigma DMAIC (Define-Measure-Analyze-Improve-Control) methodology. The 5 Whys analysis promotes fact-based analysis grounded in logical thinking rather than intuitive judgment.
Practical Example of 5 Whys Analysis
Nonconformity: A shipped product had scratches
Why? — The inspection failed to detect the scratches Why? — The inspection procedure was unclear Why? — The procedure manual was outdated Why? — No system for updating procedure manuals was established Why? — The importance of document management was not shared throughout the organization
Only by drilling down this far does it become clear that the solution must address not just the individual inspector but the entire organizational system.
2. Cause-and-Effect Diagram (Fishbone Diagram, Ishikawa Diagram)
When visualizing cause-and-effect relationships, the “cause-and-effect diagram” (fishbone diagram or Ishikawa diagram) is highly effective. This method was developed in the 1960s by Kaoru Ishikawa, a pioneer of quality management in Japan, and is widely recognized as one of the seven basic tools of quality control. The phenomenon (nonconformity) is represented as the fish’s head, with causes classified as bones branching off, ensuring comprehensive identification of multiple elements. Subsequently, each cause is investigated in depth to identify true root cause candidates.
Cause-and-effect diagrams are often used in conjunction with 5 Whys, and applying the 5 Whys analysis to each factor enables identification of even deeper root causes.
Major Category Classification Models
Depending on the industry and nature of the problem, the following frameworks are utilized for classifying factors:
| Model | Categories | Primary Application Areas |
|---|---|---|
| 6M | Man (People), Machine, Method, Material, Measurement, Mother Nature/Environment | Manufacturing, production processes |
| 5M | Manpower (Personnel), Machine, Method, Material, Measurement | Manufacturing (when environmental factors are minimal) |
| 4M | Man, Machine, Method, Material | Basic manufacturing process analysis |
| 8P | Product, Price, Place, Promotion, People, Process, Physical Evidence, Policies | Service industry, marketing |
| 4S | Surroundings, Suppliers, Systems, Skills | Service industry, IT processes |
Detailed Description of 6M Categories
The 6M model, most commonly used in manufacturing, defines each category as follows:
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Man/Manpower (People, Personnel): Worker skills, training, experience, qualifications, fatigue, motivation, communication. Human factors often emerge as results of the other 5Ms and are relatively rarely identified as standalone root causes.
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Machine: Production equipment, material handling equipment, tools, software (which may be a separate category in some industries), equipment maintenance status, machine capability.
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Method: Procedures, techniques, processes, work instructions, regulatory requirements (which may be a separate category in government agencies or heavily regulated industries).
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Material: Raw materials, parts, consumables, their quality, supply consistency, storage conditions.
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Measurement: Inspection equipment, measuring devices, data collection points, calibration status, accuracy and reliability of measurement methods.
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Mother Nature/Environment: Physical conditions affecting the work environment such as temperature, humidity, lighting, noise, vibration, workspace, and cleanliness.
These categories should be applied flexibly, with additions, deletions, or name modifications recommended based on the problem’s nature and industry characteristics. The important point is to enable the team to comprehensively understand the problem and systematically examine all potential causes.
3. Data-Driven and On-Site Reality-Based Approach (Genchi Genbutsu)
Rather than proceeding with analysis based solely on assumptions or impressions, on-site observation (Go & See, or Genchi Genbutsu: actual place, actual thing, actual situation), along with verification of related data and records, is essential. By going beyond perfunctory questioning and conference room discussions to actually visiting the site where the phenomenon occurred and directly confirming the facts, oversights and erroneous assumptions can be prevented.
This on-site-focused approach is a fundamental principle of the Toyota Production System and lean manufacturing, and is an indispensable element of effective root cause analysis. By actually observing problems on-site, interviewing those involved, and confirming processes, important insights often emerge that would not be visible in a conference room.
Problem-Solving Utilizing Root Causes: Toward Effective Countermeasures
Once the cause analysis reaches the root cause, the countermeasures implemented must also address that fundamental level. For example, merely adding “cautionary notices” to address the superficial problem of “using outdated procedures” does not constitute a fundamental solution. What is needed are recurrence prevention measures such as improving the document management system, ensuring thorough communication throughout the organization, and establishing regular document review processes.
ISO 9001:2015 also requires reviewing the effectiveness of corrective actions. In other words, organizations must not only implement countermeasures but also confirm that these measures actually prevent recurrence of the nonconformity, update risk and opportunity assessments as necessary, and make changes to the quality management system.
Patience is required to reassess whether countermeasures truly address the root cause and, if necessary, to restart the analysis from a different perspective. It is also important to consider whether similar nonconformities might occur elsewhere or in other processes. This enables organizations to leverage lessons learned from one nonconformity for organization-wide improvement.
Utilization of Digitalization and AI
Modern root cause analysis is evolving through digital tools and AI technologies. Cloud-based platforms enable distributed teams to collaboratively create and edit cause-and-effect diagrams in real time. Additionally, machine learning algorithms accelerate the analysis process by recognizing patterns in historical problem data and suggesting potential cause categories based on similar cases.
However, digital tools remain supplementary; on-site observation, team brainstorming, and judgment based on understanding the organizational context remain indispensable.
Conclusion
Identifying root causes goes beyond mere “emergency treatment” of phenomena; it becomes the foundation for organizational capacity building and continuous improvement. By utilizing 5 Whys analysis and cause-and-effect diagrams, maintaining an on-site-focused approach, and clearly distinguishing between superficial causes and root causes, true recurrence prevention and high-value-added business operations become possible.
International standards such as ISO 9001:2015 provide a framework for implementing root cause analysis systematically and effectively. Corrective actions must be appropriate to the effects of the nonconformities, requiring a risk-based approach that addresses everything from minor issues to serious safety concerns.
Cause analysis upon nonconformity occurrence should be viewed not as mere investigation but as an opportunity for development, and organizations should proactively engage with it. Through root cause analysis, organizations can transform problems into learning opportunities and build more robust and resilient quality management systems. By fostering a culture of continuous improvement and encouraging all employees to actively participate in problem-solving and prevention, organizations can enhance overall competitiveness and customer satisfaction.
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