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.