| Xbar & R Control
Charts are probably the most
widely used type of Variable Control Charts
in Statistical
Process Control.
They are used as a pair, the Xbar (Mean)
chart plots the mean of subgroups that are
taken periodically from the process. The
R (Range) chart plots the range of the subgroups.
See 'Rational
Subgroups' for guidance on
how to select subgroups.
The control limits are calculated from:
| Upper
Control Limit |
|
| Lower
Control Limit |
|
| R
Charts |
|
| Upper Control
Limit |
|
| Lower Control
Limit |
|
The factors are taken from standard
tables.
|
