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control chart for attributes and variables

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  • #45724

    Taylor
    Participant

    1) How does the Control Chart for Attributes (p chart and c chart) differ from the Control Chart for Variables?
    2) Advantages and disadvantages of using p chart.     Advantages and disadvantages of using c chart.
    3) and can i have some examples of industries that use this type of control chart?

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    #150049

    Ken Feldman
    Participant

    Wow, those are pretty basic questions and it is apparent you know very little.  So, here are some simple answers.
    1.  Control charts for attributes monitor attribute data and Control charts for variables monitor variable data.  Now do a little study on your own and find out what attribute data is and what variable data is.
    2.  If you knew what a p chart and c chart were you would have your answer.  The type of data determines whether you use a p or c chart or even an np or u chart.  Advantages and disadvantages are not really relevent.
    3.  All industries measuring processes over time can make use of all the control charts.
    I would suggest you do a little Google work on control charts to get the basics.  You can pick up a good quality book if you want to know a bit more.  The best are written by Montgomery or Wheeler.

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    #150050

    Marlon Brando
    Participant

    Just  to  simplify the  attribute  charts:
               Fixed             Varying
    Defects….c                  u        (charts)
    Defectives..np              p        (charts)
    Defects:A product may  have  many  defects (does not  prevent  the  product from functioning).
    Defective:The  product is  not  usable.
    Best Regards

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    #150053

    Ray Aaron
    Participant

    This is a good article about control charts
    http://www.sixsigmafirst.com/controlcharts1.htm
    Hope that this will help.

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    #150055

    Ken Feldman
    Participant

    Ray, that’s what I am talking about.  As easily as you found a good article, the original poster could have taken the same 30 seconds and found it and many others but they are too darn lazy.  It should answer his questions.

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    #150064

    BB
    Participant

    Darth is correct.  Advantages is not relevant.  Perhaps the only “disadvantage” is that you need to ensure that your data follows the assumptions of each of the associated distributions.  If not, use an XmR chart.  Although less sensitive, it does not assume a particular distribution (there are many fallacies around this, largely propagated by authors such as Montgomery).

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