Root Cause Verification - Corrective Action Effectiveness, or Root Cause Verification



Root Cause Verification

Just another thought here.
What method is recommended for corrective action effectiveness, or root cause verification (just in case they are not the same)?
I have been told in the past, to truly determine whether true root cause was found as well as if the corrective action implemented truly eliminates the cause. Is to implement CA, wait for a determined amount of time (if this is a reoccurrence then you should wait the same amount of time between the occurrences). Then you would take away the CA for the same amount of time with a higher frequency of inspection, if the problem occurs during this time, then your CA has been effective.
This takes a long time, especially if your last occurrence was 2 million parts ago or 2 years. And none of my customers would want me to keep a CAR open for that long. My customers generally give me 15 days to show a completed CA Report, but if I have a problem 1 out of 2 million times over the course of 2 years how do I verify anything within 15 days?

M Greenaway

Should we be required to verify the effectiveness of a corrective action, as if it was some special activity related to a specific non-conformance ?

Wouldnt our normal continuous monitoring of process performance, complaints, etc tell us if the problem re-occurs ?


I don't understand the problem...

Hi Avogel,

I don't really get the problem...but let me describe the situation at our plant...If there has been an non-conformity inspected at the customers site..we fill in a complaint document and take the appropiate CA...

To measure if it's effective we periodically analyse the CA's taken...and look if the non-conformity has reaccured...if it's not then we assume it was other way (like undoing the CA) is almost impossible because most of the time we can't recreate the same processes in which the non-conformity evolved....

Hope this helps...


Dear Avogel,
I think that many companies, our customers among them, confuse corrective action, which includes a root cause analysis, with remedial action. Remedial action is usually possible in 15 days, but verification of a corrective action typically takes much longer. As long as the remedial action works and the problem doesn't recur, customers don't often follow up to verify the effectiveness of your corrective action.

I think a good corrective action system includes both short term (remedial) and long term (root cause correction) actions. I think Martin's process of systemically monitoring the effectiveness of corrective actions is a good approach. You might even be selective about which ones you follow closely, based on your knowledge of your company's strengths and weaknesses.

Anton Ovsianko

Neither I see a serious problem.

We fill in a CAR form in the cource of corrective action implementation. It is N/C + C/A + C/A verification in one report. First we describe the NC in detail. Then we register, what we have decided to do with the NC (Control of non-conforming product etc..). Then we register what causes for the NC we identified. Then we put down what CA we decided to implement to eliminate the cause. Then we report on the results of the CA.

If the cause (the one we identified no matter right or wrong) is eliminated we close the NC for the time being. If not we investigate why and re-work and repeat the CA. If yes, but the NC repeats, we investigate to re-identify the cause.

The latter should be performed even if the lag between similar NC's is very long. Tehre must be a mechanism for retrieval of old NC's by keword. Otherwise we would not be able to learn by experience (mistakes).

This is how we do it.




Quite Involved in Discussions
Many times verification is an educated guess based on the CA, right or wrong. Does the CA match the root cause, is many times the verification.


Just back from a training course (on safety mgt.) given by a well-known registrar. The trainer (who has been used by this registrar for consulting work as well as training for a number of years) did not know the definition of "corrective action" as given in ISO 9000:2000, and argued that CA is not to eliminate the cause(s) of nonconformance but simply to reduce them to acceptable levels. While I can accept that the end result of CA typically achieves acceptable levels, the overall goal and definition of CA is to eliminate the cause. He would not believe me and argued voraciously against it. I told him to argue it with the ISO folks because that's the definition provided. He still refused to believe it and said he guessed he would have to "brush up" on the subject.

Scary. You'd think a trainer would know these things wouldn't you? He lost a bit of credibility in my eyes at that point. BTW, I didn't embarrass him in front of the class - the conversation took place on a break.

M Greenaway

Sounds like the understanding of common causes of variation and special causes of variation is somewhat missing here.

When a complaint is received investigation should be undertaken to establish the root cause. It should then be determined if the root cause is a common cause, or a special cause. Common cause and special cause relate to the statistical performance of the process. Typically a special cause would require that you take action on that specific incident in order to remove it, common cause would require you to take action on the system as a whole if it was perceived that the process performance was statistically above acceptable limits.

Your argument Lucinda appears to be taken with the consideration that all causes of non-conformance are special causes, and similarly the training guys argument was taken with the consideration that all causes are common causes.

I think perhaps you caould both learn from each other on this one.


No Martin, I simply was applying the definition of corrective action. . That was the basis of argument. He did not know the definition of corrective action.

Although practice in applying a corrective action system may be to differentiate between root causes of nonconformance and take different approaches in the handling of them, there is nothing in ISO 9001 that outlines this practice. Be careful when you say that such and such is the correct way for doing things, even when the practice is common. Each company will employ their own way.

The definition of corrective action is provided in ISO 9000 and it simply states that corrective action is taken to eliminate the cause of nonconformance to prevent its recurrence. I don't recall anything that qualifies this definition.
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