Process performance / capability indices describe the ability of the process to meet
the specifications. When a process is not capable of meeting specifications it is worth
investigating the potential changes such as centering the process average or other ways of
The dataset worksheet and analysis task pane are displayed.
The Cp indices are larger than the Pp indices indicating there is some variation
between the subgroups that could be eliminated from the process such as more
frequent recalibration of the automated colorimeter to reduce the drift in the
copper concentration. Reducing the variation between subgroups and centering the
process would lead to a capability ratio Cp of 1.672. Or a reduction to just 16
non-conforming units per million.