The efficiency of CUSUM schemes for monitoring the coefficient of variation
Continuous surveillance of the coefficient of variation is a quality control issue worthy of consideration in several manufacturing and service oriented companies. In this paper, we present a new method to monitor the squared coefficient of variation by means of two one sided cumulative sum type control charts. We study the run length properties of the proposed charts using a Markov chain approach. Several tables are given in order to show the sensitivity of the proposed charts for different deterministic shift sizes and their performance for the random shift size condition. The results show that the proposed control charts have attractive performance compared with some competing charts and are better in many cases. An illustrative example is discussed on a real dataset. Copyright (c) 2016 John Wiley Sons, Ltd.