Monitoring fractional nonconformance for short-run production

Quality characteristics observed in industrial processes are not always free from measurement errors. The term fractional nonconformance refers to the probability of an error-prone observation breaching the specification limits. Four new control statistics based on the fractional nonconformance concept are defined for process monitoring purposes. This work, motivated by milk products manufacturing, is tailored for short-run productions in which only individual measurements are accumulated over time. The performance of the newly defined control statistics is evaluated using simulation for both independent and autocorrelated processes. The results show that fractional nonconformance charts can be useful to monitor short-run production process, and the choice of the monitoring scheme does not heavily depend on the distribution of the quality characteristics.