Root Cause Analysis Defined

Friday, 07 March 2014
ASR Editor
3.6/5 rating (8 votes)

A convenient description for root cause would include the following three keys:
  1. It directly led to the issue, problem or failure. Taken by itself, this cause can clearly be seen as why things went wrong.
  2. If it had been eliminated or contained nothing bad would have happened. Eliminated or contained means that we should have known about it and planned for it, so something in our system needs to be identified and fixed.
  3. It can be clearly stated. Whatever we think the cause is, we can put it into words that everyone can agree with and understand.


Use these Key Questions when determining Root Cause:
  • What is the exact cause of the issue or failure?
  • What combination of process elements is involved? (Input/Process Steps/Output)
  • What system was in place that was designed to find or prevent this problem?
  • How, exactly, did that system break down?

This method is effective in the determination of how, exactly, the system broke down for the issue or failure being considered.
The basic methodology is as follows:
  1. Why did the specific issue or failure occur?
  2. Why would this "cause" occur?
  3. Repeat #2 three times, if possible, to arrive at the real Systemic root cause of the issue or failure.


The Systemic cause or "system failure" is important because without changing the system we can never be sure the issue or failure will not occur again.


Issue or Failure:
Joe's car won't start
  1. Why won't it start? The battery is dead.
  2. Why is the battery dead? The lights were left on.
  3. Why were the lights left on? Joe got home late and was so tired he forgot to turn them off.
  4. Why didn't they turn off by themselves? The computer chip that controls the automatic light off function in Joe's car was not working.
  5. Why was the chip not working? It failed, the check engine light came on, but Joe decided not to have the car checked.

Root Cause:

Joe did not have the car checked when the check engine light came on. This is the Systemic Failure

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