Quality Control charts moving average

Control charts based on variable sample data include the x chart and the. v chart. When dealing with a numerically measurable quality characteristic, the x chart is usually employed to monitor the process average and the s chart is used to monitor the process variability. When there is only one observation in each sample, the individual measurement chart (I chart) and moving range chart (MR chart) are used to monitor the process average and variability. It should be noted that due to the poor... 

The control charts discussed earlier are very useful in the diagnostic aspects of quality process improvement. They can be used to stabilize a process by identifying out-of-control situations. After the process is stabilized and brought in control, further improvement of the process can be achieved by using some special control charts such as the cumulative sum (CUSUM) control chart and the exponentially weighted moving average (EWMA) control chart. These control charts can be used when small shifts in a process are of interest. 

Figure 6 Quality assurance control chart of an absorbance scale certified reference material, measured regularly on a high-performance reference commercial spectrophotometer, The dotted trace indicates a moving average calculation on the data, showing a possible seasonal trend in the performance of the spectrophotometer.

It should be noted that the cumulative sum (CUSUM) and exponential weighted moving average (EWMA) control charts have also been proposed for the use in high-quality processes (Yeh et al. 2008 Szarka and Woodall 2012). However, in some cases, they are very complex and complicated to understand for the practitioners. 

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