C&A’s potato chip filling process has a lower specification limit of 9.5 oz. and an upper specification of 10.5 oz. The standard deviation is 0.5 oz. and the mean is 10 oz. What will the standard deviation of the process be in order to achieve a ppm of 5000? What comes the closest?
Expert Answer
PPM of 5000 means % defectiverate of if 0.005. The % good will be 1 – 0.005 = 0.995
The zvalue for equallly distributed along mean = Normsinv(0.995+(0.005/2)) = 2.807034
The standard deviation = (UCL-LCL)/(2*z value) = (10.5-9.5)/(2*2.807034) = 0.178124