A First Course in Quality Engineering, 2nd Edition

208 A First Course in Quality Engineering

3.4.6.5  Process Capability Results

These are measured during the validation run and are compared with

expected or targeted benchmarks� Changes should be made to the process

if any shortfall occurs in the expected process capabilities or product qual-

ity� Changes to process variables or additional process controls may have

to be implemented to achieve the target capabilities specied by customers�

For measurements, the capabilities are generally specied using C

p

and C

pk

�

Customers usually demand C

p

and C

pk

values of 1�33 or greater� For attri-

butes, capabilities are specied in defects per thousand (dpt) or parts per

million (ppm)� The target capability varies with the type of product, type of