Economic Design of X Control Charts for Monitoring a First Order Autoregressive Process

• Main Authors: Antonio F. B. Costa, Fernando Antonio Elias Claro
• Format: Article
• Language: English
• Published: Associação Brasileira de Engenharia de Produção (ABEPRO) 2010-05-01
• Series: Brazilian Journal of Operations & Production Management
• Subjects: Autocorrelation; First Order Autoregressive Model; Economic Design; Control Chart; Statistical Process Control
• Online Access: http://abepro.org.br/bjopm/index.php/bjopm/article/view/77

<p>In this paper we deal with the economic design of an X control chart<br />used to monitor a quality characteristic whose observations fit to a first order<br />autoregressive model. The Duncan cost model is used to select the control<br />chart parameters, namely the sample size (n), the sampling interval (h) and<br />the control limit coefficient (k), that lead to the optimal monitoring cost. We<br />found that the autocorrelation has an adverse effect on the chart’s power, on<br />the false alarm risk and on the cost. It also increases n and h and decreases<br />k. To counteract this undesired effect we considered setting up the subgroups<br />using non-sequential observations. It is shown that this sampling strategy<br />significantly reduces the monitoring cost.</p><p> </p>