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.
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:
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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:
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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).
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