Analysis> The 5 Whys and Root Cause Problem Solving
The 5 whys is a technique to help identify the root
causes of problems. It is a problem solving technique
that is very simple but yet very effective.
simply requires that the user asks “why”? several times
The technique is called the “5 whys”
because it is the experience of its inventor, the Toyota
company, that “why” needs to be asked successively five
times before the root cause is established.
It is a
simple but very effective technique.
It relies on a questioning attitude. Never accept
the first reason given; always probe behind the answer.
It goes along with the philosophy that a defect or
problem is something precious; not to be wasted by
merely solving it, but taking full benefit by exposing
the underlying causes that have led to it in the first
place. Many believe that it is this unrelenting
seeking out of root causes that have given the Japanese
motor industry the edge on quality, reliability and
An example is as follows:
A door does not appear to close as well as it
Because the alignment is not perfect. Why?
Because the hinges are not always located in exactly
the right place. Why?
Because, although the robot that locates the hinge
has high consistency, the frame onto which it is
fixed is not always resting in exactly the same
Because the overall unit containing the frame is not
stiff enough. Why?
Because stiffness of the unit during manufacture
does not appear to have been fully accounted for.
the real solution is to look at the redesign of the unit
Perhaps there are even more whys.
Why did this happen in the first place?
(Insufficient cooperation between design and
manufacturing.) Why so? (It was a rushed
priority.) Why? (Marketing had not given
sufficient notice.) Why? And so on.
A variation of the 5 Why technique is the “5 How”
This is often used in tracing the cause of a failure in
a product or in service delivery. (“How did that
happen?””….). The thinking and procedure is exactly the
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