Control diagram of Shewhart phase I to monitor dispersion process.

Abstract

Control diagram is a tool of Statistical Process Control (SPC) used to detect ‘in control’ or ‘out of control’ process. Practically, SPC can be done in two phases; phase I (start up) and phase II (establish). Control diagram of Shewhart is generally more suitable in the application of phase I because it is better to detect big changes. However, its control limits must be examined. This study describes control diagram of Shewhart varians S2 Fase I based on False Alarm Probability (FAP) and Attained False Alarm Rate (AFAR) to monitor process dispersion with assumption that the process is in normal distribution by unknown mean and varians. The obtained control diagram will be applied on process dispersion control for airplane components.