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SPC charts suitable for dependent data? E.g numbers on waiting list over time

Discussion in 'SPC - Statistical Process Control' started by Patrick McKeown, Jul 23, 2021.

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  1. Patrick McKeown

    Patrick McKeown New Member

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    Should you use Spc charts for dependent data? I was told it is not suitable and a run chart should be used instead. Example below

    Numbers of people on a waiting list by month. If jan there were 100, feb 120, March 135 etc. The numbers are not new patients, they are the total numbers on the waiting list, therefore marchs number of 135 is dependent on febs number.

    In this case is Spc and ucl/lcl relevant?
     
    Patrick McKeown, Jul 23, 2021
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  2. Miner

    Miner Moderator Staff Member

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    It really depends on your goals. For true "process control" it is more effective to to use SPC on the process inputs (independent data) than on the output (dependent data). However, if your goal is simply monitoring to detect changes, there is no reason than you cannot use a control chart on the output.
     
    Miner, Jul 23, 2021
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    Patrick McKeown likes this.