iSixSigma

RCA

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  • #55807

    Pravin Biradar
    Participant

    Root cause analysis is done for special causes or common causes? If we consider that we don’t have any control on special causes, same is true with some of the common causes as well? Please guide.

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    #201795

    Amit Kumar Ojha
    Participant

    Dear Pravin,
    First of all RCA is a very generic term and given its wide use it can be used for both type of causes. However, I would like to understand where is it written that special causes can not be controlled or same for common cause. I suggest you are missing the whole purpose of six sigma.

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    #201796

    Pravin Biradar
    Participant

    Thanks Amit. Let us take an example of reaching office on time. While reaching, I may come across some protests etc. which is special cause and I have no control on it hence I can not take action. Also I need to wait at 5-6 signals on the way which is a common cause, here also I can not take any action. Pl suggest.

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    #201797

    Mahmoud Tolba
    Guest

    I am supporting Pravin opinion.

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    #201798

    John
    Participant

    You can do root cause analysis and solutioning on both types of causes. The way you approach solutions is different in most cases. Cost, frequency, risk and reward all play a factor in what you want to do and how much effort you put into a solution.

    The general rule is you wouldn’t change your process for an infrequent special cause. You might just employ some countermeasures or identification and avoid criteria.

    For frequent common cause issues, typically if you want to improve your process you would change the current process permanently with your solutions.

    In your example of special cause protests you still can take action, such as taking a day off, taking a different route, if the protest is planned and you knew the day before. You probably wouldn’t change your everyday route if the protests were a one time thing. If you worked in Washington DC near the White House then these probably would be common cause and you might alter your route permanently to avoid them.

    For your stop light example. Definitely common cause within your drive to work process. Once again you can take several different actions to minimize delays. Are the lights on a timed change? If so, you could do some research and optimize your departure time to take advantage of green lights. You may get some special cause issues, emergency vehicles, funeral etc but most days your timing would be accurate. You could also plot different routes and time them to see which ones are both fastest, and most consistent in drive time. The fastest may also be the least consistent based on other special cause or common cause factors. If you were at risk of losing your job you might leave earlier, take the most consistent route and still meet your goals with less risk to time.

    Bottom line is you always have something you can do (analysis) with either type of cause. The real question is what does it cost (time, effort, money), and is the solution worth the cost…or can you accept the risk when you run into something ‘special’.

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    #201799

    Chris Seider
    Participant

    No control over special causes? I can’t imagine having such a defeatist attitude toward problem solving.

    One should learn to mitigate the response of the Y’s to the special cause events OR manage the process to not allow the root causes into the event.

    I’m not talking about “force majeure” but I don’t accept the statement of no control of special causes. Have you read the principles of SPC–which say one responds to special causes and get the process back in control.

    My two cents.

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