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On Allocation of Spares at Component Level versus System Level
Harshinder Singh and R. S. Singh
Journal of Applied Probability
Vol. 34, No. 1 (Mar., 1997), pp. 283-287
Published by: Applied Probability Trust
Stable URL: http://www.jstor.org/stable/3215194
Page Count: 5
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Design engineers are well aware that a system where active spare allocation is made at the component level has a lifetime stochastically larger than the corresponding system where active spare allocation is made at the system level. In view of the importance of hazard rate ordering in reliability and survival analysis, Boland and El-Neweihi (1995) recently investigated this principle in hazard rate ordering and demonstrated that it does not hold in general. They showed that for a 2-out-of-n system with independent and identical components and spares, active spare allocation at the component level is superior to active spare allocation at the system level. They conjectured that such a principle holds in general for a k-out-of-n system when components and spares are independent and identical. We prove that for a k-out-of-n system where components and spares have independent and identical life distributions active spare allocation at the component level is superior to active spare allocation at the system level in likelihood ratio ordering. This is stronger than hazard rate ordering, thus establishing the conjecture of Boland and El-Neweihi (1995).
Journal of Applied Probability © 1997 Applied Probability Trust