One-Sided Shewhart-Type Charts for Monitoring the Coefficient of Variation in Short Production Runs

Monitoring the coefficient of variation (CV) is an effective approach toStatistical Process Control when the process mean and standard deviationare not constant but their ratio is constant. Until now, research has notinvestigated the monitoring of the CV for short production runs. Viewedunder this perspective, this paper proposes a new method to monitor theCV for a finite horizon production by means of one-sided Shewhart-typecharts. Tables are provided for the statistical properties of the proposedcharts when the shift size is deterministic. Two illustrative examples aregiven in order to illustrate the use of these charts on real data.