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What is 5 Whys and how can I use it?

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  • Community Leader

Hi all,

The other day we discussed about how important it is to have a Defect Elimination process established in order to stop the fire fighting and improve your results.

We also mentioned a few techniques that can help you to understand your failures and their root causes so that you can establish an action plan to avoid its reoccurrence.

This week we will be discussing about one of those techniques: 5 Whys.

So, what is 5 Whys?

5 Whys is a problem-solving technique that became popular in the 1970s, as part of one of the most famous production systems in the world, the Toyota Production System.

Basically, it consists on approaching any issue by asking “why” a few times. This is because, the answer for the first “why” will lead you to another “why”, which the answer will trigger another why, and so on.

How should I use it?

As the vast majority of the problem-solving techniques, you start looking at the consequence of the problem, aiming at the root cause in the end – always working backwards.

You start asking why that issue happened, and will keeping asking the same question (why) repeatedly until you find the root cause.

For instance:

1-      Why have we lost 5 hours of production?

         - Because our critical pump broke down.

2-      Why has this pump broken down?

          - Because we did not know this would happen

3-      Why we did not know this would happen?

          - Because we did not identify any failure symptoms.

4-      Why did we not identify any failure symptoms?

          - Because we do not have any inspection routines.

5-      Why don’t we have any inspection routines?

          - Because we don’t have a PM Program.


When can I use it?

It does vary on person to person. Some like using 5 Whys as a standard technique, while other prefer using it for simple problems and using other problem-solving techniques for more complex situations. Generally speaking, the is not a rule of thumb for this question, essentially you can use it for any situation as long as it clarifies the root cause of the problem.


Have you used 5 Whys before? Do you use any specific triggers for picking 5 Whys or a different technique when facing a failure?



Raul Martins


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5 Whys is a powerful tool that was a big help to me digging deeper into problems.  The limitation I see to it and with some other approaches is the focus on a single cause.  I've stopped using 5 Whys for the most part and instead use cause mapping.  There is a nice template and website at ThinkReliability.com that is based on Excel and free to use.  They also have many free video tutorials and PDF examples that you can look through.  I feel the strength of the cause map is focusing on the facts of the event without worrying about categorizing or a strict chain.  You can add multiple causes and probe deeper into each one.  Many times this yields solutions that aren't initially apparent.

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@Raul MartinsThanks for outlining this topic.

We are using 5whys after conducting FTA and shed the light more into the root cause and is really helpful at certain degree specially with KPI performance but it does have limited usages when it comes to holistic process investigation consists of multiple aspects such as e.g.technical , leadership and competencies..... so I recommend TapRoot but is required little skills to drive its benefits.



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  • Community Leader

Hi @Chuck Clarkson and @Mohammed tawili,

I agree with you about the limitations of the 5Whys.

Yet, I see it as a good solution in two different scenarios:

1- You have no defect elimination process and need to start understanding and eliminating failures;

2- You have a well-implemented defect elimination process with different triggers. For instance, it can be used in minor failures (up to 1 hour downtime?) analyses by properly trained staff members, such as Maintenance Technicians and Operators. While for major failures, another technique can be used by Engineers. By doing so, you will have more failures analysed (reducing the reoccurrence likelyhood).

In terms of the cause mapping, I haven't heard about it before. But it seems to be a good RCA tool as well. I will have a better look at it later this week.



Raul Martins

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Hi @Raul Martins,

I agree that 5Y is very suitable for the environments where they are starting with the use of RCA techniques. It may fall short for more complex analyses. I was normally using a three-legged 5Y (3L5Y) analysis, which provides more insights, as you dig into the specific, detection and systemic root causes in each respective leg.

After finding a specific root cause, it is the additional aspects (detection and systemic) that bring all pieces of the puzzle together for a true understanding of the cause(s). After applying the right corrective actions, not only are the original issues fixed, the corresponding detection system and management system gaps that allowed the issue to occur in the first place, are identified and resolved. By finding a true systemic root cause and fixing it, a massive leverage for the organisation is created as fixes spread across the plant and are incorporated into future programs. That is why the 3L5Y has a substantial advantage over a traditional 5Y method.

In my experience we have often combined the 3L5Y with Ishikawa (fishbone) analyses, or used one of the two, depending on the specific situation, which allowed for a more flexible approach.

As to the triggers; in many cases we have used RCA for:

  • Events with substantial consequences (OHS, environmental, quality, economic, reputational),
  • Equipment failures with substantial consequences,
  • Near-misses that could have resulted in substantial consequences,
  • Repetitive equipment failures,
  • Maintenance rework,
  • Customer complaints,
  • Internal non-conformities (system, process, etc.).

Or whenever  it was deemed necessary by line managers, or requested by first-line supervisors. It is helpful if management defines a threshold for what “substantial” actually means in more specific terms.

Should anyone be interested in a nice explanation of concepts and use of different RCA techniques, a free IAEA document can be downloaded at: https://www-pub.iaea.org/MTCD/Publications/PDF/TE-1756_web.pdf. True that the document is prepared for the NPPs in the first place, yet the concepts can be used in other industries, as well.




Edited by Andrej
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  • Community Leader

Hi @Andrej,

Interesting approach for the 5Whys technique. This allows a wider understanding of the failure and its cause(s), which tackles part of the issues we mentioned before.

Thank you for the IAEA document! It is great to have all of those RCA techniques in a single place.


Raul Martins

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