Finding the Root Cause With 5 Whys

5 whys

When performing root cause analysis, the main goal is to eliminate the problem once and for all using a long-term solution. While a short-term solution is enticing and gives immediate gratification, it only temporarily puts the problem on hold. The root problem remains and will have to be dealt with in the future.

To avoid this pitfall, Six Sigma allows us to do process improvement the right way. By using the DMAIC (Define Measure Analyze Improve Control) methodology for process improvement, we can perform root cause analysis in the Analyze phase and get to the bottom of the problem.

In the Analyze phase, the team looks at the production process and identifies problems that can cause defects. One of the key tools used to find the root cause in this phase is the 5 Whys.

How 5 Why Helps with Root Cause Analysis

With the 5 Whys, all you need to do when a problem arises is ask “Why” five times in order to get to the root cause of the problem. You don’t need to ask five times (it can be more or even less), but five is a good rule of thumb.

Each “Why” is essentially meant to reveal the problem within the problem. Eventually, there will be a “Why” that uncovers the root cause since you won’t be able to ask “Why” anymore.

Using 5 Whys

There’s no special technique used in 5 Whys. Here are the steps:

  • Identify the problem and write it down (make sure to describe it completely)
  • Ask why the main problem happened and write the answer next to it
  • The team discusses if that is the root cause
    • If it is, the root cause has been identified
    • If it is not, the team must repeat this step (as many times as it takes) until the root cause is identified 


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