Get to The Root Cause Using 5-Why Analysis

Posted by on Jan 4, 2011 in Uncategorized | 0 comments

The 5 Whys is a questions-asking method used to explore the cause/effect relationships underlying a particular problem. Ultimately, the goal of applying the 5 Whys method is to determine a root cause of a defect or problem.  It was developed at Toyota as part of their production process.

Often a 5 Why analysis is done at three different levels:  the specific nonconformance; why the problem was not detected; and what systemically occurred that created the problem.

Some of the Whys can be answered using current process knowledge, but usually a more in-depth analysis will be needed to get to the true root cause.  This can include the use of other basic quality tools.

Here is an example of using the 5 Whys in an admin area:

Observation:  Our revenues were down 12% this quarter.
Why?:  Because we sold fewer products, and the price stayed the same.
Why?:  Our advertising presence was down 25%.
Why?:  The ad budget request wasn’t received in time.
Why?:  There was no advertising manager.
Why?:  The position wasn’t posted as open for two months after the initial opening.
Why?:  The manager of the advertising area was delinquent in sending the opening to personnel.

Note that Why was actually asked 6 times in this example to get to the root cause.

Once you’ve determined the root cause using the 5 Why process, you can use the therefore technique to make sure it makes sense.  Using the admin example above, it would flow like this:

The manager of the advertising area was delinquent in sending the opening to personnel.
Therefore:  The position wasn’t posted as open for two months after the initial opening.
Therefore:  There was no advertising manager.
Therefore:  The ad budget request wasn’t received in time.
Therefore:  Our advertising presence was down 25%.
Therefore:  We sold fewer products, and the price stayed the same.
Therefore:  Our revenues were down 12% this quarter.

Keys to using the 5 Why process effectively are to make sure you start with a good problem description, confirm each cause before going to the next Why, reverse the process using the therefore technique, and verify all cause-effect relationships.

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