Thoughts on root cause analysis -part 1

I find myself thinking quite a bit about problem solving and root cause analysis because I enjoy the topic so much. One topic that always stirs much discussion is the topic and flawed belief that there is always “ONE ROOT CAUSE” to a problem. The quality toolbox is filled with many tools for conducting root cause analysis such as 5 Whys, fishbone diagram, Tree Diagram, etc…The 5 Why is a perfect example of this linear thinking approach that leads one to believe that there is one single cause, or that if you ask “Why” 5 times you will always arrive at a root cause. I am not knocking the 5 Whys approach as I believe it is necessary to ask why so as to not jump at the first “symptom”. I do believe however, that you have to use these tools with some common sense. Here is an example:

Problem – Car won’t start when leaving for work in the a.m.

Possible causes – dead battery, alternator, fuel filter plugged, fuel pump  not working, clogged fuel injector, etc.. (note I am not a mechanic)

You test the battery and it is dead (do you replace the battery and move on?). Let’s assume you do that and a day later it is dead again. Uh-oh, not enough root cause done. You find that the alternator is bad. The car has 90.000 miles on it, but why did it fail? Do you replace it and move on or do you dig even deeper?

Possible next level of causes of failed alternator – OEM suggests replacing it after xxxx miles (which you did not do). Is that the cause? Do you dig even further to find out exactly what failed in the alternator? “Why”? Most would not. Why? – it is beyond your scope of controllable variables typically. So by not taking it as far as humanly possible for example to the design level are you truly finding the “ONE ROOT CAUSE”, or are you stopping at a convenient spot on the “Cause and Effect Chain”? You can control changing the alternator out at the recommended interval, but not necessarily the design (sure you can complain, but it did meet the warranty most likely).

This same things happens in the manufacturing world when there is a problem. We stop at one of the following Cause and Effects points:

1) A cause that has come up in the past (familiarity and a ready made fix exists)

2) A cause that is within the sphere of our influence (maybe our dept., but what if it goes beyond that)

3) Only looking at the immediate issue or defect that occurred (Process Root Cause) but not continue and look at why the defect escaped our detection and was shipped to a customer (Detection Root Cause). Also – there are many times “Systemic Root Causes”. I will discuss Detection Root Cause and Systemic Root Cause in my next blog. 

Sorry about the length of this one but I love thie topic.

Happy Problem Solving!

Mark

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About markqualitynetzel

Quality Management professional with over 27 years experience in manufacturing (metal stamping, assembly, fabrication, welding, coatings, molding) and training.

Posted on August 27, 2011, in Uncategorized. Bookmark the permalink. 5 Comments.

  1. Hello Mark,
    My name is Muthu. I read your blog on RCA-1. Just 2 days back I had posted a question on the ASQ Linkedin group on this topic RCCA.

    http://www.linkedin.com/groupAnswers?viewQuestionAndAnswers=&discussionID=67984946&gid=3633&commentID=49917125

    What percentage of companies do you think do true RCCA? It can be a time consuming process but worth it. How does the stakeholders respond when they are asked to do a RCA?

  2. 5 Why is very useful. In many cases, people knows its use but doesn’t use this method.

  3. Hi Mark,

    good work man. keep doing it. Looking to hear more from you.

    Thanks,

    SK Vel.

  4. Hi Mark,
    I agree completely. Quite often I find that there are several causes to a non conformance. Usually, any one of them is not serious, but added together, create an issue that can cause an unacceptable non-conformance, and one that is hard to fix! This is because fixing just one issue is not enough to fix the whole situation. So, one is forced to continue the C/A process, sometimes over and over again, until the problem is solved. At that point, one finds that several items have been addressed to finally correct the inital problem. The down side to this situation is that you sometimes are not really sure what fixed the problem. You just list all the corrections and revisions and hopefully make good product from then on.
    Looking forward to part 2 of RCA.
    Paul Mencke

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