The 5-Whys – and Root Cause Analysis | Quality Management

Mostly employed in root cause analysis, 5 Whys prominently appears in the Analyze phase of DMAIC in Six Sigma. This technique iteratively interrogative in nature, mainly used to identify to the root cause or defect, was developed by Sakichi Toyoda and used in the Toyota Motor Corporation. [source: wiki]

Experts have varied opinions about this methodology which is often performed by a fish-bone diagram. There is no single root cause, if observed closely. Usually, it is a chain of events or combination of factors. Identification of the bug is a critical challenge and there are various methods and techniques. One such identified method is 5-why. This helps to understand the top 5 root causes which predominantly contribute to the problem .

The method might sound basic but very effective. The question is often posed from the answer received and it’s an iterative model. You can try and picture as some day-to-day issues you find yourself troubleshooting by find the root cause, like the scores of your child in a recently held d test paper. It’s as much questioning your child “why did you grades dip?” and from response offered by your child, there is a counter question –answer, till you are convinced one way or the other.

 Why did your grades dip?

I didn’t do the exam properly

 Why didn’t you do the exam properly?

I couldn’t answer most of the questions

Why couldn’t you answer most of the questions?

The questions were not familiar.

Why weren’t the questions familiar?

I had not prepared well enough

Why didn’t you prepare?

Because I was playing and missed on the time to prepare

Finally, it’s the lack of preparation that led to the poor performance. This might be your conclusion drawn from the conversation.  And the advice or course of action is to ‘gear up well and be more prepared to face the next test.’

Here is another example from a professional backdrop:

Image courtesy: http://image.slidesharecdn.com/5whys-140105104229-phpapp01/95/5-whys-the-path-to-resolution-8-638.jpg?cb=1388918607 

 Apply the same to a project to analyze about a failure – which we call it the root cause analysis.

There is no rule to stop the questioning at 5-level. It can go further. General studies reveal that ‘5 why’ usually lead to the main reason(s) of failure.

To illustrate further the 5 Whys, take a look at the image below:

Picture courtesy:  http://www.educational-business-articles.com/wp-content/uploads/5-Whys-example.gif 

Limitation

This method suffers from its own share of shortfalls.  The technique stops at the symptoms level and fails to dig deeper at the lower-level root causes.  The results not being repeatable is a major constraint in this method. Besides, ‘Why’ can lead to multiple root causes but there is an inclination to isolate a single root cause and stick to it. 

The limitations aside, 5 Whys is nevertheless is significantly used in Root Cause Analysis (RCA).