1.2. SIGMA
One of the ways to measure the variation of a product or a process is to use a mathematical term called sigma. We will learn more about sigma and how to calculate this value as we proceed, but for now it is enough to know that the lower the sigma value, the smaller the amount of process variation and the higher this sigma value, the greater the amount of the process's variation. Since the sigma calculation is normally done on a computer or calculator, it is more important that you gain a sense that sigma is a measure of the data spread (variation) than it is to be too involved with the detailed actual calculation of sigma.
Ideally, the sigma value is low in comparison with the allowable tolerance on a part or process. If so, the process ...
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