When creating a Quality Management System (QMS) using the requirements of ISO 9001:2015, you will find that corrective action is one of the key elements to a good QMS. In fact, this was so important that the previous version of ISO 9001 included corrective action as one of only six mandatory documented procedures. Considering how important this process is to the success of a good Quality Management System, it is surprising that so many companies struggle to make corrective actions work to their benefit.

Root Cause Analysis: The most important part of corrective action

As has already been discussed in ISO 9001 – Difference between correction and corrective action, a correction is the action you take to perform an immediate fix of the most obvious problem to remove the nonconformity and make the product or service acceptable to use. This will take little investigation to find, and is a quick fix for this one-time problem; however, it does not take action to prevent the problem from happening again.

If you have identified that a problem is more serious than one simple non-conformance, and you need to perform corrective action to prevent the problem from happening again, you will want to use a systematic process to ensure you do not miss anything – such as the Seven Steps for Corrective and Preventive Actions to support Continual Improvement. In a corrective action process, it is critical that you do not just try to fix the easy-to-see causes; instead, you need to look deeper into the cause of the problem to find the root cause so that you can correct this.

Only when you find and correct the root cause of a problem will you truly ensure that the non-conformance does not happen again.

Some simple, yet effective root cause analysis tools

There are many ways to investigate the root cause of a problem, both intricate and simple. Two of the most commonly used methods are very simple to use once you understand how they work, and can help to ensure that you think further into a problem to find the root cause so that you can fix it; these two tools are the “5 why” and “fishbone diagram” tools.

5 why: With this simple root cause analysis tool you just start with your problem and ask “why” until you come to the ultimate cause. This may take more or less than five “whys,” but five questions will commonly come to the root of the problem. An example could be for an error that caused a part to be made that did not fit into an assembly:

  • Why did the part not fit? – The part was too long.
  • Why was the part too long? – The drawing was incorrect.
  • Why was the drawing incorrect? – The mechanical designer did not notice the interference in dimensions in the design.
  • Why was the interference not noticed? – The design process did not require a step to make this comparison.
  • The corrective action is to update the design process to include a specific step where the mechanical designer will perform an interference check in the design software before the drawings are created to ensure that all parts will fit in the assembly.

Fishbone diagram: Often called “cause and effect diagrams” or “herringbone diagrams,” this tool was first created by Karou Ishikawa in 1968 and is used as a method to organize a team to brainstorm the possible causes of a problem. It is considered one of the seven basic tools of quality.

  • All potential causes of the specific problem are listed under six main cause headings that can contribute to a problem: methods, manpower, machine, material, measurement, and environment.
  • Once all potential causes are listed, they are reviewed and eliminated one by one through investigation or experimentation until the most likely root cause is found. Sometimes there is more than one potential most likely cause identified.
  • Corrective action can then take place to address the root cause or causes identified from the analysis.


As I mentioned above, sometimes extremely complex problems will require very intricate root cause analysis methods to solve. Some examples that you might want to find out more about are: design of experiments, fault tree analysis, failure modes and effect analysis, or one of many others.

Root cause analysis: Worth the effort for systemic problems

Especially when you have a systemic problem that keeps recurring, and is costing money, resources, or customer satisfaction, you will want to make sure it does not happen again. When this happens, doing good root cause analysis as part of your corrective action process will help you reap the most benefit by solving the problem once and for all. Besides, after putting in the effort to correct a problem once, you don’t want to have to do it again.

If you want to learn more about ISO 9001, why not sign up for the ISO 9001:2015 Foundations Course?

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