How to Use the 5 Why Process for Determining Root Cause

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The 5 Why process can be an effective approach to determine the root cause of a problem or issue. The goal of asking "why" five times is to work backwards from the result to get to the cause, with each question revealing more and more specifically why the event occurred. Follow these steps to use the 5 Why method the next time you have a problem.

Collect as much information about the problem as possible. The 5 Why technique works best when you have information about the problem such as background, conditions and similar cases. This will help determine the most logical and likely answer to each question.

Assemble a team. In order to utilize the 5 Why method most effectively, you will need to assemble a team of people from different functional groups, with varied specialties and experience. A critical element of the 5 Why method is the people who are asking the questions and providing the most likely answers at each step. Having a diverse group of people means gaining insight from different viewpoints and opinions. Approaching the problem from different angles could lead to answers that you may not have thought of on your own, and ultimately reveal the root cause of the issue.

Start with the problem and ask 'why' five times.

Start with a simple problem statement about what the issue is and then start to work back from there asking why each step occurred. Use logic and the knowledge and experience of your team to find the most probable answer to each 5 Why question.

Here is an example of the process in action:

Problem Statement: Production shut down. Why did production shut down? (Why 1) The Deltron 3000 broke down. Why did the Deltron break down? (Why 2) The Automator is not functioning. Why is the Automator not functioning? (Why 3) The Automator only lasts about six months, this one hasn't been changed in eight months. Why didn't anyone change the Automator at 6 months? (Why 4) No one knew to change it. Why didn't anyone know it needed to be changed? (Why 5) There is no preventative maintenance schedule set up to tell the mechanics to do it. (Root cause.)

Analyze each of the 5 Whys. As you work through answering the 5 Whys, analyze each step and test your assumptions if possible. Ask yourself some questions about the why answers. -Would this answer lead to the previous effect? -Does this make the most sense given everything we know about the problem? -Could there be other possibilities?

Remember, the goal of the 5 Why method is to find true root cause to prevent the problem from happening again.

When you have asked why five times and think you have gotten to the root cause, find a solution that addresses that root cause. When you have a solution, follow the logic back up the why chain to determine if it will solve the problem. Continuing from the previous example:

Root Cause: There is no preventative maintenance schedule set up to tell the mechanics to do change the Automator on the Deltron 3000 every six months. Solution: Implement a preventative maintenance schedule to change the Automator on the Deltron 3000 every six months.

Implement your solution to the last why and see what the effects are. Refine your solution or repeat the 5 Why process if necessary to reassess.

It is OK to go beyond 5 Whys if necessary to determine root cause and it makes sense. For instance if Why 4 in the example was changed to, "The mechanics didn't follow the preventative maintenance schedule," then you may want to continue asking why the mechanic didn't follow the procedure:

Why didn't the mechanic follow the schedule? (Why 5) He has not been trained on the preventative maintenance schedule for the Deltron 3000. Why is the mechanic not trained? (Why 6) He just joined the area and his previous area did not have a Deltron 3000. (Root cause.) Solution: Train all new mechanics on the preventative maintenance of equipment in areas they will be joining.

You may end up finding a different solution to the problem if you continue asking why until you get to the true root cause. This will help to keep you from settling on an easy answer that just blames a person to get to the root cause. The root cause is more likely a process or procedural issue to be addressed.