The 5 whys method: how and when to use it

5 Whys method

The "5 Whys" method is a technique used to understand the root causes of a problem. It was originally developed by Taiichi Ohno, the chief engineer of the Toyota production system.

The concept is simple: when a problem arises, you ask the question "why?" five times. Each answer to a "why" forms the basis of the next question. This allows you to go beyond the symptoms of a problem and reach its root cause.

How to apply the "5 Whys" method

Main steps

To properly apply the "5 Whys" method, here are the main steps to follow:
  1. Define the problem: Start with a clear and specific description of the problem. It may be helpful to gather as much information as possible about the problem, including when and where it occurs and who is involved.
  2. Gather a suitable team: Assemble a team that understands the problem and the system or process in question. Ensure you include people with different perspectives to get a comprehensive view of the problem.
  3. Ask the first "why": Ask "why" the problem occurs. Ensure the answer is based on facts and evidence and not on assumptions or opinions.
  4. Continue asking "why": For each answer, ask the question "why" again. Continue this process until you reach a cause that, if addressed, could prevent the problem.
  5. Identify the root cause: The root cause is typically the one that, if addressed, could prevent the problem from recurring. If you're unsure of the root cause, you might need to do more research or use other problem analysis tools.
  6. Develop and implement corrective actions: Once you've identified the root cause, you can develop corrective actions to solve the problem. Ensure you set up measures to monitor the effectiveness of these actions.


How to know if you have reached the end of the 5 whys?

The "5 Whys" method is a general practice, and the number "5" is not strict. You might reach the root cause in fewer than five questions or need more than five questions. The idea is to keep asking "why" until you reach a cause that, if addressed, could prevent the problem.

Here are some criteria that might indicate you have reached a root cause:

  1. The identified cause is something you can control or influence. If the cause is out of your control, it's likely not the root cause.
  2. The identified cause, if addressed, could prevent the problem from recurring. If addressing the cause doesn't prevent the problem from recurring, it's probably not the root cause.
  3. The identified cause is specific and doesn't refer to general or vague issues.
  4. The cause has a human origin. A controllable or influenceable cause has humans behind it. These people can improve a process, a tool, a control, or even a strategy.
  5. You cannot ask further "why" questions that would make sense or provide additional relevant information.

It's important to note that even after identifying a potential root cause, it might be necessary to check if addressing that cause truly prevents the problem from recurring. In some cases, there might be multiple root causes that all need to be addressed to fully resolve the problem.


Examples of the 5 Whys method

Alright, here are some examples of the 5 Whys method applied to problems in the production and sales domains.

Example in the production domain

Problem: A factory's production line has stopped.

  1. Why? Machine B stopped working.
  2. Why? Machine B overheated.
  3. Why? The machine wasn't properly lubricated.
  4. Why? The maintenance schedule wasn't followed.
  5. Why? The operators weren't trained on the importance of following the maintenance schedule.


Potential solution: Provide appropriate training to the operator team and implement a reminder system for maintenance tasks.


Example in the sales domain

Problem: Sales of a specific product decreased over the last quarter.

  1. Why? There was a drop in traffic on the product's page on our website.
  2. Why? Online advertisements for the product received fewer clicks.
  3. Why? The conversion rate of the advertisements decreased.
  4. Why? The content of the advertisements is no longer as engaging as before.
  5. Why? The images and messages of the advertisement haven't been updated for a long time and no longer reflect current consumer preferences.


Potential solution: Update the images and messages of the advertisement to match current trends and consumer preferences, and regularly monitor the performance of the advertisements.

When to use the 5 Whys, and its limitations

The 5 Whys method generally applies well to problems that seem to stem from a singular and linear cause. That is, when you have a clearly defined problem that can be broken down into a sequence of causes and effects. It's especially useful for technical or mechanical problems but can also be used in other contexts like operational processes or project management.

Here are some situations where this method may be limited:

  1. Complex or systemic problems: For problems that have multiple causes or result from complex interactions between different parts of a system, the "5 Whys" method might not be sufficient. It tends to oversimplify problems by assuming a single linear cause, which isn't always the case.
  2. Lack of prior knowledge: The "5 Whys" method relies on the investigator's knowledge of the problem. If the investigator doesn't understand the system or process well, they might not be able to ask the right questions or correctly identify the root cause.
  3. Weakness in considering human or organizational problems: The "5 Whys" method is sometimes criticized for its tendency to focus on technical problems and overlook human or organizational issues.
However, it can be used in these situations if complemented by other methods suited for these cases. For instance:
  • during a root cause analysis process like the Ishikawa diagram. Then, the 5 Whys technique can be used to deepen a cause.
  • in the "Define" phase of DMAIC to start identifying potential causes of the problem.

Key success factors for applying the "5 Whys" method

Here are some key success factors for applying the "5 Whys" method:

  • Team commitment: The commitment of the team is crucial for the success of the "5 Whys" method. The team must be willing to actively participate in the discussion and share their knowledge and perspectives.
  • Objectivity and focus on facts: It's important to remain objective and focus on facts when applying the "5 Whys" method. Avoid assumptions and unfounded opinions.
  • Follow-up and verification: Once you've identified the root cause and implemented corrective actions, it's important to follow up and verify the effectiveness of these actions. If the problem reoccurs, you may need to revisit your analysis or consider other possible causes.
  • Patience and perseverance: The "5 Whys" method requires patience and perseverance. It may be necessary to ask "why" more than five times or to go back and ask questions again to get a clear understanding of the root cause.
  • Recognizing when another method is needed: The "5 Whys" is a simple and effective tool, but it's not always the best approach for every problem. It's essential to understand its limitations and know when to turn to more sophisticated or complementary analysis tools.


The "5 Whys" method is a simple yet useful tool for identifying the root causes of problems. However, its simplicity can be limiting when facing more complex problems that require additional analysis tools. In these cases, it can then be used within methods better suited to these problems, like DMAIC, 8D, or organizational diagnostics.


Do you work in a high-performance organisation?
Find out if your company or team is using the best management practices by answering Wevalgo's self-assessments

Become an improvement leader within your team by sharing your analyses


Click on one of the following buttons to start

You will benefit from the expertise of management consultants who have implemented these best practices with thousands of managers around the world. Wevalgo puts this know-how, secretly guarded by traditional consultancies, at your service.

Evaluate your clients' practices if you are a consultant.    

You may also access our unique directory of by function and industry

Stay Informed

When you subscribe to the blog, we will send you an e-mail when there are new updates on the site so you wouldn't miss them.

Related Posts



No comments made yet. Be the first to submit a comment
Already Registered? Login Here
Thursday, 25 April 2024