Moving Average and Moving Range Control Chart
Moving Average & Moving Range Control Chart

The Moving Average and Moving Range charts provide a graph of the moving average of a process characteristic and the moving range extent. The moving average is computed as the average of a sample of successive measurement points. The number of points averaged equals the subgroup size. A new average is computed for each successive point by throwing away the oldest point and including the next in sequence. Think of a sliding cell whose width is equal to the subgroup size moving across the data in sequence order, point by point. At each new point a new moving average is computed and plotted. The Moving Average chart gives a picture of how well a process is centered and if it is stable.