A true process Cpk of 1.5 is a goal that all managers and all quality engineers would like to achieve and maintain, but even then there is still some statistical room for problems. At a Cpk of 1.5, your defect rate is 3.4 ppm. If your annual production is 10 million units, you can therefore expect approximately three defects per month, despite the fact that you are maintaining SPC on a capable process. Once managers understand the probability of defects even in capable, controlled processes, they must decide whether to sink more capital into further improving the Cpk, or cope with the small number of defects that will be produced by the process in its current state. The common thread to coping with these misconceptions is education.
Good managers are willing to learn and apply their learning.
They can be good supporters of quality once they get their facts straight. Your job as quality engineer is to make sure that they do, and not let management by fable govern your company's decision processes. Select another article. Return to Quality Magazine's home page.