|Reactions to out-of-control conditions
||If the process is out-of-control, the process engineer
looks for an assignable cause by following the out-of-control action plan
(OCAP) associated with the control chart. Out-of-control refers to rejecting
the assumption that the current data are from the same population as the
data used to create the initial control chart limits.
For classical Shewhart charts, a set of rules called the Western Electric
Rules (WECO Rules) and a
set of trend rules often are
used to determine out-of-control.