| XmR Control
Charts (also known as ImR Control
Charts) are Individual and Moving Range
Charts. They are used when the subgroup
size is one. This may be when logistic reasons
prevent larger subgroups, but is more commonly
when there is no basis for rational subgroups.
The chart is based on the moving range
between consecutive samples:
| Upper
Control Limit |
|
| Lower
Control Limit |
|
| Moving
Range Chart |
|
| Upper
Control Limit |
|
| Lower
Control Limit |
|
D4 and d2 are taken
from standard
tables, based on a subgroup
size of 2:
|
