| 1. |
- Bergman, Bo, et al.
(författare)
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A family of test statistics for detecting monotone mean residual life
- 1989
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Ingår i: Journal of Statistical Planning and Inference. - : Elsevier BV. - 0378-3758 .- 1873-1171. ; 21:2, s. 161-178
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Tidskriftsartikel (refereegranskat)abstract
- The mean residual life of a life distribution F with survival function F̄=1-F is defined as e(x)=(sh{phonetic}∞xF̄(t)dt)/F̄(x) if F̄(x)>0 (e(x)=0 if F̄(x)=0). The function e(x) has proved to be of great interest in many different areas such as biometry, reliability and social sciences. The class DMRL (IMRL) consists of those life distributions which have decreasing (increasing) mean residual life; i.e. e(x) is a decreasing (increasing) function of x. In this paper we present and study a family of test statistics intended for testing exponentiality against DMRL (IMRL). The family includes the test statistics proposed for the same purpose by Hollander and Proschan (1975) for complete samples and later generalized by Chen et al. (1983a) to accomodate randomly right censored samples. We compare the efficiency for different members in the family of test statistics when testing against some different alternatives. Furthermore, we study the efficiency loss due to different amount of exponential censoring. The asymptotical normal distribution of the test statistics are presented and the quality of the normal approximation is also discussed
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| 2. |
- Klefsjö, Bengt
(författare)
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Testing against a change in the NBUE property
- 1989
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Ingår i: Microelectronics and reliability. - : Elsevier BV. - 0026-2714 .- 1872-941X. ; 29:4, s. 559-570
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Tidskriftsartikel (refereegranskat)abstract
- A life distribution F with survival function F=1-F, finite mean μ and mean residual life e(t) is said to be NBUE (NWUE) if e(t)⩽(⩾)μ for t⩾0. This NBUE (NWUE) property can equivalently be characterized by the fact that φ(u)⩽(⩾)u for 0⩽u⩽1, where φ(u) is the scaled TTT-transform of F. A generalization of the NBUE and NWUE properties is that there is a value of s such that φ(u)⩾u for 0⩽u⩽p and φ(u)⩽u for p⩽u⩽1, or vice versa. This means a trend change in the NBUE property. This generalized aging property is called the NBUE-NWUE property. In this paper the authors present and study a test statistic intended for testing exponentiality (i.e. φ(u)=u for 0⩽u⩽1) against this NBUE-NWUE property. The asymptotic normality of the test statistic, suitably normalized, is established and a simulation study is presented (20 refs.)
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| 3. |
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| 4. |
- Kumar, Uday, et al.
(författare)
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Reliability investigation for a fleet of load haul dump machines in a Swedish mine
- 1989
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Ingår i: Reliability Engineering & System Safety. - : Elsevier BV. - 0951-8320 .- 1879-0836. ; 26:4, s. 341-361
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Tidskriftsartikel (refereegranskat)abstract
- The recent trends of deployment of complex and capital intensive equipment in mines has created interest in the field of maintenance and operational reliability of this equipment. The failure consequences associated with random equipment failures have considerable influence on the total operating cost of a highly mechanized mining system. Keeping this in view, a reliability investigation was initiated for a fleet of diesel operated load-haul-dump (LHD) machines in a Swedish mine. The goal is to estimate the operational reliability of these machines, locate items or assemblies which need improvement in design to enhance the reliability and to decide the duration of optimal preventive maintenance. Failure data for one year of LHD machines are analysed using the recently developed graphical technique of total time on test (TTT) plotting. Analytical methods like Kolmogorov-Smirnov test and maximum likelihood estimation are used in the analysis. The importance of testing the reliability data for the presence of trends and serial correlation is also emphasized.
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