2. Process variability

The use of simple statistical techniques to manage a manufacturing process enables:

• to prevent the effects of disruptions rather than suffer them and sort production after the fact;

• to avoid 100% inspection (inspection of all units produced);

• to streamline sampling plans (number and frequency of checks) rather than choosing them "based on experience" (often on a whim).

These statistical techniques use the evaluation method by checking a sample limited to a few units (n) to estimate the average value and dispersion of all units produced. For the selected characteristic X, the value $\overline{x}$...