Monitoring multivariate process variability when sub-group size is small

• Main Authors: Djauhari, M. A., Sagadavan, R., Li, L. S.
• Format: Article
• Published: Taylor and Francis Inc. 2016
• Subjects: QA Mathematics
• Online Access: http://eprints.utm.my/id/eprint/71991/; https://www.scopus.com/inward/record.uri?eid=2-s2.0-84974679299&doi=10.1080%2f08982112.2016.1166386&partnerID=40&md5=5099d53c450a1ade8aa39dab325e4108
• Institution: Universiti Teknologi Malaysia

ABSTRACT: The current practice of multivariate process variability monitoring, when sub-group size is small, has nothing to do with probability of false alarm (PFA). Consequently, the reliability of the existing control charts remains undetermined. In this article, we propose a control chart which is reliable, very sensitive to the change in variance for small or moderate correlation, and provides a root causes analysis of an out-of-control signal. To illustrate these advantages, an industrial example is presented and the results are compared with those issued from the existing methods.