Checkline FH Series - Manual (Page 61)

© ElektroPhysik MiniTest 7200 FH / MiniTest 7400 FH 61
Process capability index (Cp)
The cp index is a measure of the spread of the readings as related to the specification limits. Only
the spread is of importance here. The cp index is calculated as follows:
s
LSGL USL
Cp
6
−
=
where USL = Upper specification limit
where LSL = Lower specification limit
Process capability index (Cpk)
In addition to the spread, the cpk index also takes into account the location of midpoint as related
to the specification limits.
s
LSL x
Cpku
3
−
=
s
x USL
Cpko
3
−
=
Cpk = Min
{
Cpkl, Cpku
}
where USL = Upper specification limit
where LSL = Lower specification limit