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Topic Difference between run chart and control chart

Difference between run chart and control chart

Home Forums Old Forums General Difference between run chart and control chart

This topic contains 2 replies, has 3 voices, and was last updated by Profile photo of Nilanjan Sarangi Nilanjan Sarangi 8 years, 8 months ago.

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  • #148619

    Can anyone tell me how is a run chart diffetent from a control chart


    Basically, a run chart does not have an average line or control limits.
    For variable data, a run chart also does not have a chart for the dispersion variable (range or s).
    Often a run chart is used for individuals rather than for averages. This makes it less predictable, since averages will follow a normal distribution, while individual abservations may not. 


    The purpose of the two are totally different.
    If you are starting to study a process, you start with run chart. You go down to the process, measure responses and plot them in order and anlyse using the no. of runs at the end of data calculation. Here, the guiding factor is the median line. So, you do NOT analyse or decide on the data real time, rather at the end of it. And through this, you know, whether there is/are assignable cause(s) present or your process is behaving purely under chance cause. This would guide you to select the right approach to reduce variations in the process parameters / results.
    On the other hand, a control chart is designed to use in real time during a process to warn / pre-warn when an assignable cause starts to kick in. To design and use control charts, you need a good amount of data from your process. To draw the control lines, you need to have measured the data.
    To summarise, both are wonderful tools. Run chart is an investigative tool, mostly used in the initial phases of projects to decide on approach to improve it; Control chart is pre-warning control tool, mostly used in maintenance of the process before or after it has been improved.
    Hope it is useful :-)

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