Sains Malaysiana 42(7)(2013):
981–987
Modeling Repairable System Failure with Repair History
and Covariates
(Model Sistem Kegagalan Dibaiki dengan Sejarah Pembaikan dan Kovariat)
Samira Ehsani*
Department of Mathematics, Faculty of Science, University Putra
Malaysia
43400, Serdang, Selangor D.E. Malaysia
Jayanthi Arasan & Noor Akma Ibrahim
Laboratory
of Computational Statistics and Operations Research, Institute for Mathematical
Research
University Putra Malaysia, 43400, Serdang, Selangor D.E. Malaysia
Diserahkan: 4 Mac 2010/Diterima: 2 Februari 2013
ABSTRACT
In this paper, we extended a repairable system model under general
repair that is based on repair history, to incorporate covariates. We
calculated the bias, standard error and RMSE of the parameter estimates of this model
at different sample sizes using simulated data. We applied the model to a real
demonstration data and tested for existence of time trend, repair and covariate
effects. Following that we also conducted a coverage probability study on the
Wald confidence interval estimates. Finally we conducted hypothesis testing for
the parameters of the model. The results indicated that the estimation
procedure is working well for the proposed model but the Wald interval should
be applied with much caution.
Keywords: Covariate; general repair; repairable system
ABSTRAK
Dalam kertas ini, kami melanjutkan model sistem dibaiki di bawah
pembaikan am yang berdasarkan sejarah pembaikan, dengan menggabungkan kovariat.
Kami mengira ralat, sisihan piawai dan PMRKD bagi penganggar parameter-parameter
model ini pada sampel yang berbeza saiz dengan menggunakan data simulasi. Kami menguna pakai model ini kepada data demonstration sebenar dan
telah menguji kewujudan kecenderungan masa, kesan pembaikan dan kovariat. Berikutan itu kami juga menjalankan kajian liputan
kebarangkalian bagi anggaran selang keyakinan ‘Wald’. Akhirnya
kami menjalankan pengujian hipotesis bagi parameter-parameter model. Keputusan yang diperoleh menunjukkan bahawa prosedur penganggaran
berjalan lancar bagi model yang dicadangkan tetapi selang ‘Wald’ harus
digunakan dengan berhati-hati.
Kata kunci: Kovariat; perbaikan umum; sistem
diperbaiki
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*Pengarang
untuk surat-menyurat; email: ehsani_samira@yahoo.com
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