One-sided run rules control charts for monitoring the coefficient of variation in short production runs

This paper proposes a new efficient method to monitor the coefficient of variation (CV) in a short production run context by means of one-sided run rules type charts. Plotting points on run rules control charts is a stochastic process modelled in this paper by using Markov chains to get their main statistical properties. Proofs concerning the computation of the truncated run length properties are given. Tables summarising the main numerical results for several combinations of in-control CV values, sample sizes and shift sizes are provided. Moreover, a comparison analysis has been performed to show that implementing one-sided run rules type charts is the best decision most of the time. Finally, an example illustrates the use of these charts on real data.