Root cause analysis is an important step to enable companies to make the right changes in order to prevent faults from happening over and over again. Too often we find ourselves in a situation where we think we have performed a good root cause analysis and still we are confronted with the same issue again. The question is why? Didn’t we execute the root cause analysis right? Or did we implement the wrong preventive measures? What is the root cause of failure in our root cause analysis?
Why ask five times WHY?
The 5 WHY analysis is a simple and very effective technique. By repeatedly asking the question WHY, you can peel away the layers of symptoms which can lead to the real, underlying root cause of a problem. Sometimes you will need to ask the question fewer or more times than 5 before you find the issue related to a problem. Some Quality Managers find it very important that you write down exactly 5 times WHY. If you don’t they are not amused, but it is about finding the root cause of the problem and not about how many times you ask yourself the question. It is just a tool that can help you, not a dogma!
How to use the 5 WHY analysis?
Here are some easy steps to effective perform a 5 WHY analysis:
- Write down the problem. Writing helps you to formalize the problem and describe it completely. If you work with a team, it also helps the team to focus on the same problem.
- Ask yourself why did the problem happen and write down the answer.
- Ask yourself – looking at your answer – again why did the problem happen, and write down the answer.
- And again, ask yourself – looking at your answer – why did the problem happen.
- Ask yourself this question as often as necessary until the team agrees that the problem’s real root cause is identified. This may take fewer or more times than 5 WHYS.
5 WHY Example and template
Below we will shod an example of a 5 WHY analysis on an issue where glass was in the finished product at a client:
- Why did the client find glass in our product? Because one of the light bulbs broke at line 5. Now you know where it happened.
- Why did the light bulb break? The forklift truck broke the light bulb when the driver was removing a pallet. Now you know who was responsible for breaking the light bulb.
- Why is it possible for the driver to break the light bulb? The space is too narrow for the driver to turn the forklift.
- Why is the space too narrow for the forklift? The light is hanging from a long cord.
- Why is the cord so long? It was designed this way, but it can be adapted. Solution found: adapt the length of the cord.
- Why is it possible that the glass is found in the finished product? The light bulb broke after the sieve. We don’t have another possibility to put a sieve in line 5.
- Why was production not stopped according to the procedure? The forklift drive was not aware of the procedure.
- Why was the forklift driver not aware of the procedure? We do not train people on the glass policy.
- Why don’t we train people on the glass policy? We thought it was common sense anyway. Second preventive measure: regularly train all staff in the glass policy.
Below you see a picture of one of many templates you can use:
Create Powerful 5 WHY’s by combining it with a fishbone analysis
The 5 WHYS can be used individually or as a part of the fishbone or Ishikawa diagram (see picture below for an example). You typically start exploring the problem with the fishbone analysis and after that you perform a 5 WHY analysis on each of the sub items in your fishbone diagram. When this is done you really will force the organization to dig deep enough and find the root cause!
Benefits of the 5 WHY analysis combined with fishbone
The 5 WHY analysis combined with fishbone analysis has very powerful benefits:
- It helps you to identify the root cause of a problem
- It can determine the relationship between different root causes of a problem
- It really is one of the simplest tools you can use.
- It is ease to complete without statistical analysis
- The combination makes sure you do not focus on one strand of analysis only using 5 WHY analysis.
5 WHY analysis in itself is already a very strong tool for root cause analysis, but combining it with a fishbone analysis you really have the most powerful, yet easy to use and implement combination of tools for root cause analysis.
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