
Statistical
Methods
Applied
to
Quality
Control
119
a difficult enough job, and both parties must be fully committed to achieving
low (ideally zero) PPM values.
In order for the PPM approach to have any hope of success, the equip-
ment manufacturer has to be relied on to return defective components to the
component manufacturer (or supplier) together with all the pertinent infor-
mation regarding operating conditions, circuit functions and design changes,
etc. Rejects will have to be verified and the supply volume must be large
enough over a sufficient period of time for the PPM value to be of any
real use. Accurate analysis of rejects and faults will allow ...