5 Whys: The Ultimate Root Cause Analysis Tool
The 5 Why process is one of the most powerful tools for problem-solving and improving quality. It works by asking "why" five times, which forces people to consider the root cause.
Many problems are caused by poor communication. If we ask why something was happening, it is observed that it would often lead to a better understanding of what was going wrong.
This method helps identify the root causes of any problem.
There is an oil spill on the workshop floor. To find the root cause, you ask why five times.
Why 1: Why do we have an oil spill? ... The lubricating oil pump is leaking.
Why 2: Why is the pump leaking? ... The pump gasket got damaged.
Why 3: Why did the gasket get damaged? ... Because it was a substandard gasket.
Why 4: Why do we have a substandard pump gasket? ... Because it was purchased from an unapproved supplier.
Why 5: Why did we purchase it from an unapproved supplier? ... Because we have the policy to go for the lowest bidder.
As you would see, the problem goes much deeper into the company policy of buying spare parts.
Rules of performing a five whys analysis
The 5 Whys is an iterative questioning technique designed to uncover the root causes of problems. The following steps outline how to use the 5 Whys technique:
1) Ask "Why?" Find out why this happened.
2) If you still don't know what's causing the problem, ask again. Repeat until you get to the bottom of the issue.
3) When you are done with the analysis, take action to prevent future occurrences.
Criticism of Five Whys Technique
Some people feel that this approach is an over-simplification of problem-solving. For any event to happen, there is always more than one cause. This approach only considers a single reason for any issue.
In the example above, when we asked question 3, why the gasket was damaged, the response was that the gasket was of substandard material.
In the real-life, there could be multiple reasons for the gasket failure, such as:
- It was not correctly installed by the maintenance group.
- It was over-tightened.
- The maintenance schedule was not followed, as this gasket was supposed to be replaced long ago.
- etc, etc.
However, we just considered one reason for the gasket failure in the five whys analysis.
Do we always need to ask why five times?
No. Five is a good number to start. You really do not need to ask why exactly five times. Repeat asking why till you reach the root cause of the problem. You should stop when the action required to address the reason goes beyond your scope of authority.
For example, in the example of the oil spill above, you could keep asking why and end up with action to replace the Purchasing Manager or even the company's CEO.