There is Only One Way to Identify the Root Cause

Quality Quiz:
What is the best way to identify the root cause (major cause) of variation in the process creating a defined problem? You must choose only one answer.

a. The Cause-and-Effect Diagram (also known as Fishbone or Ishikawa Diagram)
b. The Pareto Diagram
c. The 5 Ws and 2Hs
d. The 5 Whys
e. Brainstorming
f. Voting
g. Just blame your supplier and let them figure it out
h. None of the above

The correct answer is (h) none of the above. Why? Because all these methods are widely used to help identify or organize potential root causes or the most likely cause. However, none of them actually can identify the root cause.

The only way and best way is by testing and verifying. Without data to prove that it is a root cause, you only have a list of possible root causes. The root cause will be verified when you can pull it in and out of the process resulting in the problem appearing and disappearing. Think of it as a light switch that can turn the light on and off on command.