Inequalities involving the lifetime of series and parallel systems |
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Authors: | William E. Stein Ronald Dattero Roger C. Pfaffenberger |
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Affiliation: | 1. Department of Business Analysis and Research, College of Business Administration, Texas A & M University, College Station, Texas 77843;2. Texas Christian University, Fort Worth, Texas 76129 |
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Abstract: | Let {Xi} be independent HNBUE (Harmonic New Better Than Used in Expectation) random variables and let {Yi} be independent exponential random variables such that E{Xi}=E{Yi} It is shown that documentclass{article}pagestyle{empty}begin{document}$ Eleft[{uleft({mathop {min ,X_i}limits_{l le i le n}} right)} right] ge Eleft[{uleft({mathop {min ,Y_i}limits_{l le i le n}} right)} right] $end{document} for all increasing and concave u. This generalizes a result of Kubat. When comparing two series systems with components of equal cost, one with lifetimes {Xi} and the other with lifetimes {Yi}, it is shown that a risk-averse decision-maker will prefer the HNBUE system. Similar results are obtained for parallel systems. |
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