Question about Service Call Measurements

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    Are more aggressive targets used in control charts where the process being measured is by definition a defect? For instance, in our case service calls occur when the customer experiences a defect. Our n = number of instances where the customer experienced a defect. Should these metrics have more aggressive limits than for example a metric on a manufacturing production output. Thank you in advance.



    Why should the targets be more aggressive, a process is still a process whether it is manufacturing or transactional and should be treated the same.  You just need to make sure you use the correct type of control chart for your data.  In your case the data is discreet, i.e. a count of defects, therefore you should use a C-Chart below is the text from Minitab help on the subject.  You will need to decide what your subgroup size is, perhaps calls per day would be appropriate.
    Stat > Control Charts > Attributes Charts > C
    Tracks the number of defects and detects the presence of special causes

    . Each entry in the specified column contains the number of defects for one subgroup, assumed to have come from a Poisson distribution with parameter m. This value is both the mean and the variance.
    By default, the process average number of defects, m, is estimated from the data. This value is the center line on the C chart. Minitab also uses this value to calculate the control limits.



    In order to answer your question I would have to ask why you are measuring the customer service call process?  There are two basic reasons for doing that.
    1.  To show your process is in control
    2.  To change your process by reducing the number of service calls thus reducing cost and improving customer satisfaction.
    If  your measurements are meant to drive down customer service calls at what level would you claim complete success (100, 10, 0)?  If your goal is lower than what manufacturing is currently injecting into the system then your measurements will generate action in the manufacturing process because to reach your goal they must change their output.   
    The bottom line is your goals, your control limits, and your measurments should be set to drive change in manufacturing’s behavior.  If you set your control limits at their current control limits will that drive change in the manufacturing process and thus the number of customer service calls?  Only you can answer that!



    I do not know if you are still out there or not since you posted this 2 weeks ago and no one responded ’til now, but…
    Please sit back take a deep breath and realize I am only trying to help!
    There, now I have that out of my system.  The control limits on control charts are derived from the data you have collected.  They are not set, they are not used to show aggressiveness.  If you can get a copy of Understanding Statictical Process Control by Wheeler and Chambers and read it, I think you will better understand the purpose of control charts and their limits.  If you have already read it, I do not know why you are asking this question, unless someone else has pointed you down this road.  If that is the case, stay away from this person/s for the rest of your SPC life.  If you need help you might try addressing Vinny, Darth, Mike Carnell, or the Stans specifically in a post.  

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