PDF
…just
experiencing normal variation versus when something out of the ordinary is
occurring? Control charts were designed to make that distinction
As long as all points lie inside the upper and lower control limits, the variation is
presumed to be normal or a common cause variation. When a data point falls
outside those limits, it’s time to look for a…
https://www.wichita.edu/industry_and_defense/NIAR/Documents/400_Wednesday_Ng.pdf