5 why method - how to

Probably you have experienced it yourself, a problem that pop-ups again and again in one form or another.  The actions that are taken every time the problem occurred seem not sufficient enough to let the problem disappear permanently. This happens when the root cause which causes the reoccurrence has not be found and tackled properly. Instead, a "solution" is created which focuses on the symptom of the problem. Often this happens when people jump to conclusions.

The 5 why method is used to find the root cause of a problem. it is used to find the relationship between the symptoms or effect of a problem and the underlying root cause. The 5 why method encourages people to avoid assumptions and instead trace the chain of causality from the symptoms of the problem all the way to the root cause.

The root cause is the fundamental reason why the problem occurs. Solving the root cause will fix the problem permanently, reducing the likelihood of recurrence to a minimum or preferable zero. 

Actionable root cause

In order to solve the root cause, you should be able to control the cause AND you should be able to do this with a reasonable amount of resources. not enough time, not enough investments, or not enough manpower can therefore never be the root cause. In order to avoid these answers, you could ask yourself why did the process fail instead of just why.

Let's illustrate this by some examples.

A person has fallen because he has slipped over an ice spot. You could say that he has fallen due to the fact that it is freezing, but you have no control over the weather.  Imagine that after using the 5 why method you realize that the root cause is that the person did not have the right shoes. This is a valid root cause since this is something that we can control. We can buy new shoes for the person.

A webshop his packages are often delivered later than the agreed delivery date. Maybe you defined as the root cause that the shipping times are too long.   This is something which you can control but often reducing shipping time, such as using express delivery,  increases the shipping cost. It could be that the extra cost is not reasonable. another way to look at the problem is by saying that the root cause is that the delivery dates are not set properly. this is something which you can control in a reasonable way.

Be aware that there can be more then one root cause.

The 5 Why method: simple and efficient

The 5 why method is a simple but efficient tool to reveal the root cause. In the 5 why method the question, why something has happened, is repeatedly asked for increasingly going in-depth and finally find the root cause. The 5 represents the number of times you generally have to ask the question before getting to the root cause.

Before asking the first why you have to assemble a team to get the most out of your 5 why exercise. You should involve the people who have hands-on experience with the process where the problem occurs and the people who are experiencing the problem. Make sure you identify a person as the facilitator. Possibly you can combine the 5 why method together with making the fishbone diagram. This can be created within the same team.

Make certain that everyone understands the problem statement and agrees with it before you start the 5 Why. You can use the 5W1H method for this.

Use a whiteboard or flip chart to write down the different why's. Although the method speaks of 5 why you can ask the question more (or less) times if needed. Once asking the question why does not generate useful answers anymore, you know it is time to stop. If you think you found already the root cause after 2 or 3 times asking why you should ask yourself the question is this really the root cause?

Fact-based answers

Asking why should simple but answering it right can be challenging. Be certain that the answers actually happened otherwise your whiteboard or flip chart would become quickly cluttered. This means you have to verify that the answer is correct before moving to the next one. It could be possible that you need to collect data or set-up a test in order to verify your answer.  And finally, be certain that there is a real cause and effect relationship between your answer and the why question. this can be done by reversing the order and use the " and therefore" expression. 

lets illustrate this with and example.

  • The problem statement: The car did not start
  • Why: because the battery was dead
  • Verified: The battery voltage has been measured with a volt-meter and was too low
  • Cause and effect relationship: the battery was dead and therefore the car did not start makes sense

Not all problems have a single root cause. Because of this,  Sometimes you will find out that more than one answer is valid. If this is the case you can create an extra branch for the other answers and ask further why questions for each branch.

Blame the process not the people

The 5 why method helps also with finding what is wrong with the process instead of blaming people. Often a problem occurs due to a human error. But processes can be prone to human error. Asking, why the human error occurred, could reveal underlying problems within the system. For example, people who do repetitive tasks could easily miss one of the steps they have to perform in a while if there is no checklist. The root cause should always be linked to a failing process and not a person.

5 Why example

Finally lets look at an example:

the problem statement:  The pizza was delivered to late

  1. Why: the pizza was not ready in time at the kitchen
  2. Why: the kitchen ran out of ingredients
  3. Why: there was higher demand than expected
  4. Why: there was an promotion they were not aware off
  5. Why: lack of communication between management and kitchen staff

We could even go further and ask the why question a sixth, seventh, or even more times. Remember we have to stop once we do not get any useful answers anymore.

This article was updated on November 30, 2022