Generalize for large production runs
Discover Deming, the theory of variations

The examples we have taken are typical of process monitoring indicators (in the ISO 9001 sense), or global production indicators.

The technique described remains valid, but would become tedious for the observation of large-scale processes. In this case, the best approach is to set up the process using the technique described, on 100 to 1,000 samples, identify and deal with special causes of variation, and once the process is stable, carry out only periodic monitoring of the process on small samples (typically 3 to 10 parts). This periodic monitoring ensures that the process remains stable (and therefore predictable): this is Statistical Process Control (SPC), described in the...