Each data point, MR i , is the moving range of the x values in each group. MR i is not plotted for i < w because it is undefined.
Term | Description |
---|---|
MR | moving range |
w | Number of observations in the moving range. By default, w = 2. |
The center line is the unbiased estimate of the average of the moving range.
center line = MR * d2(w)
The LCL is the greater of the following:
or
Term | Description |
---|---|
d2() | a constant used to estimate the standard deviation |
w | number of observations in the moving range. By default, w = 2. |
σ | process standard deviation |
k | parameter for Test 1 (default is 3) |
d3() | A constant used to estimate LCL and UCL. |