iSixSigma

Run Chart

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  • #41576

    aparna
    Participant

    While running the measure phase in a DMAIC Project, if p value for cycling/trending<0.05 should we remove those data points after investigation?

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    #130490

    Kumar
    Participant

    No Aparna. You should not remove those data points. These are only data paoints of your present process. You need to improve the process and then do the analysis again and then can see whether there is an improvement.
    Normally, these data points will lead you to patents.
    Is it clear? If not, contact me in [email protected]

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    #130503

    aparna
    Participant

    Thanx Mr Kumar. But would need further clarification.I had made run chart, in the measure phase. DMAIC deals with improving the process if the process has common causes. Since run chart has trending and cycling value as p is less than 0.05, dont we have to remove the points which lead to the special cause before starting the analyse phase.

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    #130504

    Ron
    Member

    Why are you using a run chart instead of a control chart? Suggest you utilize the data you have and contruct the appropriate Control Chart.
    You should always investigate out of control data points and only when you have a root cause and a solution in place that precludes the recurrence of the defect should you consider removing the data point.

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    #130506

    aparna
    Participant

    Thanx Ron.
    I hv used the IMR Control Chart, which showed 6 points to be out of control. 2 points went out of control as those were Bank Holidays, hence response was not within the cycle time.
    But no info I could gather for the other 4 points which went out of control

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    #130509

    BTDT
    Participant

    Aparna:Rather than ignore the data points corresponding to bank holidays, use the Excel function, “=NETWORKDAYS(Start_Date,End_Date,Holidays)” to calculate the execution time. You may define your own definitions of holidays.We used this function to calculate whether the cycle time for processing documents was less than 24 hours based on an eight hour day, and a five day work week and included holidays.It also gave us the benefit of smoothing the execution time, rather than having blank entries for anything between 8 and 16 hours each day, and large gaps over the weekends. The customers were aware the 24 hour specification limit was in terms of work time, not time on the clock.The resultant control chart showed the process was under control, although we still had a DPMO of 816,000. When we showed the process capability calculation to the management, they could not object to the extreme values as outliers and ignore the fact that the process was extremely poor.Include all the data for this calculation, you may find some of the points are no longer out of control. The ones that remain as such should be investigated.Cheers, BTDT

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    #130599

    AB
    Participant

    BTDT – Thanks. I’ve never used networkdays function before. I always copied the data into Microsoft Project and calculated elapsed duration as MS Project has a fairly good scheduling tool with the ability to not only enter holidays but also have different calendars including rotational shifts, personnel absentism, etc.; but always wondered if there was a better way
    Thanks
    AB

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