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5 Whys Problem Solving

The 5 Whys problem solving technique uses a very simple iterative approach in analysing and attempting to find the root cause of a problem. The 5 why technique originates from the Toyota Manufacturing system pioneered in Japan by the Toyota car company. The concepts consist of defining the problem in a problem statement first and then asking why is this is the case, or why is the problem what it is. This technique is sometimes approached in a team environment and can involve brainstorming as an idea generation process to identify potential causes.

Once the most immediate cause has been identified for the first effect or symptom of a problem and written down, you repeat the process of asking why this is the case or this cause itself is caused by what? The process continues for five times or until the root cause has been reached, thus giving it the name 5 whys. Research has shown it usually takes an average of five times to reach the actual root cause.

The 5 Whys technique is sometimes criticised as being too simplistic and can at times lead to incorrect conclusions on the root cause of a problem. The technique is suited for simple problem solving, but larger more complex issues should be handled with a more thorough technique although the 5 whys can initially be used to generate potential causes of some problems and to stimulate the thought process.

An example of a 5 Why problem solving exercise

In the following example of a production issue the 5 why problem solving technique is appropriate to use due to the most likely cause of the problem needs to be found quickly and is likely to not require a complex fault finding process.

Production Problem Example:

A production process in the food manufacturing sector which produces potato chips in a continuous production line and has a production issue where during testing of production samples the potato chips salt levels are too high consistently in all samples taken over the last hour. A solution for this issue must be found promptly as due to being food manufacturing all production out of spec is not able to be sold.
Example of 5 Why problem solving

Fig1. Application of the 5 Why problem solving Technique to aid production problem analysis

In the example above we have reached a possible root cause for the production problem by asking Why? three times, this will vary depending on the problem being analysed. Below are the investigation and corrective actions which must be carried out to confirm the root cause as true. If the possible cause is found to be incorrect then the Why can be repeated until the true root cause is identified.

In some cases a cause or answer to one of the Why's can itself be caused by several issues or failures. In the example above, the failure of the feeding equipment could also be caused by incorrect weight readings from the salt feed bin to the process controller or failure of the process controller as well. In the case either of these could be a reasonable failure suspect then it could also be listed as a separate cause in the 3rd Why section of the diagram as a separate branch to keep the iterative process going for this potential cause to identify if this is the root cause.

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