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Mathematical Problems in Engineering
Volume 2005 (2005), Issue 1, Pages 1-6

On the coefficients of variation of uptime and downtime in manufacturing equipment

1Manufacturing Systems Research Laboratory, GM Research & Development Center, Warren 48090-9055, MI, USA
2Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor 48109-2122, MI, USA

Received 28 November 2004

Copyright © 2005 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


It was reported in the literature that the coefficients of variation of uptime and downtime of manufacturing equipment are often less than 1. This technical paper is intended to provide an analytical explanation of this phenomenon. Specifically, it shows that the distributions of uptime and downtime have the coefficients of variation less than 1 if the breakdown and repair rates are increasing functions of time.