A First Course in Quality Engineering, 2nd Edition

Quality in Production—Process Control II 347

defects per million (DPM) of total units even in the worst condition when the

process center is 1�5σ distance away from the target�

Thus, a 6-sigma process with its center on target produces only 0�002 DPM

and will produce, at most, 3�4 DPM at the worst possible condition of the

process center being away from target by 1�5s distance� Such a process was

designated as the benchmark for minimum variability�

For the sake of uniformity, any process that produces less than 3�4 DPM,

whether the process produces a characteristic that can be measured or an

attribute characteristic that can be counted, is