Select the method or formula of your choice.
In This Topic
Plotted points
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.
Notation
| Term | Description |
|---|---|
| MR | moving range |
| w | Number of observations in the moving range. By default, w = 2. |
Center line
The center line is the unbiased estimate of the average of the moving range.
center line = MR * d2(w)
Notation
- MR
- the estimate of the average moving range for the method that you use to estimate the standard deviation
- d2(w)
- the unbiasing constant given in this table
- w
- the number of observations that are used in the moving range
Control limits
Lower control limit (LCL)
The LCL is the greater of the following:
or
Upper control limit (UCL)
Notation
| 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. |
