Confidence interval procedures for system reliability and applications to competing risks models

2013 ◽  
Vol 20 (2) ◽  
pp. 161-184 ◽  
Author(s):  
Yili Hong ◽  
William Q. Meeker
Keyword(s):  
Confidence Interval ◽  
Competing Risks ◽  
System Reliability

Fuzzy System Reliability Analysis Based on Confidence Interval

2012 ◽  
Vol 433-440 ◽  
pp. 4908-4914 ◽  
Author(s):  
Ezzatallah Baloui Jamkhaneh ◽  
Azam Nozari
Keyword(s):  
Confidence Interval ◽  
System Reliability ◽  
Fuzzy System ◽  
Statistical Data ◽  
Parallel Systems ◽  
Fuzzy Data ◽  
Statistical Methodology ◽  
Fuzzy Reliability ◽  
Numerical Examples ◽  
Cut Set

This paper proposes a new method for analyzing the fuzzy system reliability of a parallel-series and series-parallel systems using fuzzy confidence interval, where the reliability of each component of each system is unknown. To compute system reliability, we are estimated reliability of each component of the systems using fuzzy statistical data with both tools appropriate for modeling fuzzy data and suitable statistical methodology to handle these data. Numerical examples are given to compute fuzzy reliability and its cut set and the calculating was performed by using programming in software R.

scholarly journals Reliability Inference for the Multicomponent System Based on Progressively Type II Censored Samples from Generalized Pareto Distributions

Mathematics ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 1176
Author(s):  
Lauren Sauer ◽  
Yuhlong Lio ◽  
Tzong-Ru Tsai
Keyword(s):  
Maximum Likelihood ◽  
Confidence Interval ◽  
System Reliability ◽  
Bootstrap Method ◽  
Multicomponent System ◽  
Type Ii ◽  
Censored Samples ◽  
Generalized Pareto ◽  
Pareto Distributions ◽  
Generalized Pareto Distributions

In this paper, the reliability of a k-component system, in which all components are subject to common stress, is considered. The multicomponent system will continue to survive if at least s out of k components’ strength exceed the common stress. The system reliability is investigated by utilizing the maximum likelihood estimator based on progressively type II censored samples from generalized Pareto distributions. The confidence interval of the system reliability can be obtained by using asymptotic normality with Fisher information matrix or bootstrap method approximation. An intensive simulation study is conducted to evaluate the performance of maximum likelihood estimators of the model parameters and system reliability for a variety of cases. For the confidence interval of the system reliability, simulation results indicate the bootstrap method approximation outperforms over the asymptotic normality approximation in terms of coverage probability.

scholarly journals Dementia, Alzheimer’s Disease, and Mortality after Hemodialysis Initiation

2018 ◽  
Vol 13 (9) ◽  
pp. 1339-1347 ◽  
Author(s):  
Mara A. McAdams-DeMarco ◽  
Matthew Daubresse ◽  
Sunjae Bae ◽  
Alden L. Gross ◽  
Michelle C. Carlson ◽  
...  
Keyword(s):  
Risk Factors ◽  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Confidence Interval ◽  
Competing Risks ◽  
Older Patients ◽  
Disease Diagnosis ◽  
Hazard Ratio ◽  
Old Patients ◽  
Diagnosis Of Dementia

Background and objectivesOlder patients with ESKD experience rapid declines in executive function after initiating hemodialysis; these impairments might lead to high rates of dementia and Alzheimer’s disease in this population. We estimated incidence, risk factors, and sequelae of diagnosis with dementia and Alzheimer’s disease among older patients with ESKD initiating hemodialysis.Design, setting, participants, & measurementsWe studied 356,668 older (age ≥66 years old) patients on hemodialysis (January 1, 2001 to December 31, 2013) from national registry data (US Renal Data System) linked to Medicare. We estimated the risk (cumulative incidence) of diagnosis of dementia and Alzheimer’s disease and studied factors associated with these disorders using competing risks models to account for death, change in dialysis modality, and kidney transplant. We estimated the risk of subsequent mortality using Cox proportional hazards models.ResultsThe 1- and 5-year risks of diagnosed dementia accounting for competing risks were 4.6% and 16% for women, respectively, and 3.7% and 13% for men, respectively. The corresponding Alzheimer’s disease diagnosis risks were 0.6% and 2.6% for women, respectively, and 0.4% and 2.0% for men, respectively. The strongest independent risk factors for diagnosis of dementia and Alzheimer’s disease were age ≥86 years old (dementia: hazard ratio, 2.11; 95% confidence interval, 2.04 to 2.18; Alzheimer’s disease: hazard ratio, 2.11; 95% confidence interval, 1.97 to 2.25), black race (dementia: hazard ratio, 1.70; 95% confidence interval, 1.67 to 1.73; Alzheimer’s disease: hazard ratio, 1.78; 95% confidence interval, 1.71 to 1.85), women (dementia: hazard ratio, 1.10; 95% confidence interval, 1.08 to 1.12; Alzheimer’s disease: hazard ratio, 1.12; 95% confidence interval, 1.08 to 1.16), and institutionalization (dementia: hazard ratio, 1.36; 95% confidence interval, 1.33 to 1.39; Alzheimer’s disease: hazard ratio, 1.10; 95% confidence interval, 1.05 to 1.15). Older patients on hemodialysis with a diagnosis of dementia were at 2.14-fold (95% confidence interval, 2.07 to 2.22) higher risk of subsequent mortality; those with a diagnosis of Alzheimer’s disease were at 2.01-fold (95% confidence interval, 1.89 to 2.15) higher mortality risk.ConclusionsOlder patients on hemodialysis are at substantial risk of diagnosis with dementia and Alzheimer’s disease, and carrying these diagnoses is associated with a twofold higher mortality.

scholarly journals Parameter Interval Estimation of System Reliability for Repairable Multistate Series-Parallel System with Fuzzy Data

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Wimonmas Bamrungsetthapong ◽  
Adisak Pongpullponsak
Keyword(s):  
Confidence Interval ◽  
System Reliability ◽  
Fuzzy System ◽  
Estimation Method ◽  
Interval Estimation ◽  
Parallel System ◽  
Expected Length ◽  
Parameter Interval ◽  
Sets Theory ◽  
Triangular Membership Function

The purpose of this paper is to create an interval estimation of the fuzzy system reliability for the repairable multistate series–parallel system (RMSS). Two-sided fuzzy confidence interval for the fuzzy system reliability is constructed. The performance of fuzzy confidence interval is considered based on the coverage probability and the expected length. In order to obtain the fuzzy system reliability, the fuzzy sets theory is applied to the system reliability problem when dealing with uncertainties in the RMSS. The fuzzy number with a triangular membership function is used for constructing the fuzzy failure rate and the fuzzy repair rate in the fuzzy reliability for the RMSS. The result shows that the good interval estimator for the fuzzy confidence interval is the obtained coverage probabilities the expected confidence coefficient with the narrowest expected length. The model presented herein is an effective estimation method when the sample size isn≥100. In addition, the optimalα-cut for the narrowest lower expected length and the narrowest upper expected length are considered.

An Approximate Method of Forming a Confidence Interval on Predicted System Reliability

1959 ◽  
Vol PGRQC-16 ◽  
pp. 64-69
Author(s):  
Robert E. Warr ◽  
Joseph A. Navarro ◽  
Richard Schwartz ◽  
Robert D. Turner
Keyword(s):  
Confidence Interval ◽  
Approximate Method ◽  
System Reliability

Hybrid Fuzzy Estimation of System Reliability for Multi-State System

2017 ◽  
Vol 866 ◽  
pp. 387-391
Author(s):  
Wimonmas Bamrungsetthapong ◽  
Adisak Pongpullponsak
Keyword(s):  
Confidence Interval ◽  
System Reliability ◽  
Fuzzy System ◽  
Coverage Probability ◽  
Interval Estimation ◽  
Point Estimate ◽  
Hybrid Estimation ◽  
Expected Length ◽  
Fuzzy Parameter ◽  
Fuzzy Parameters

This article is purpose a hybrid estimation of the fuzzy system reliability for the Non-repairable multi-state series-parallel system (NMSS). Considering the fuzzy parameter of NMSS are prior fuzzy parameters. Then the posterior fuzzy parameters of NMSS are constructed by fuzzy Bayesian point estimate of fuzzy system reliability. Moreover, an approach to construct interval estimation of the fuzzy system reliability of NMSS will be used in estimation of the prior fuzzy confidence interval and posterior fuzzy confidence interval of fuzzy system reliability. Finally, the coverage probability and the expected length that it is used to interpret the efficiency of both fuzzy confidence intervals are presented.

scholarly journals Αξιολόγηση οργανικών βλαβών μετά από ενδονοσοκομειακή καρδιακή ανακοπή

2018 ◽  
Author(s):  
Ιωσηφίνα Κολιαντζάκη
Keyword(s):  
Confidence Interval ◽  
Competing Risks ◽  
Cumulative Incidence ◽  
Cerebral Performance Category ◽  
Performance Category ◽  
Intention To Treat ◽  
Hazard Ratios ◽  
Cerebral Performance Category Score ◽  
Category Score

Σκοπός: Η χαμηλή δόση στεροειδών μπορεί να φανεί ωφέλιμη σε βαρέως πάσχοντες ασθενείς με σηπτική καταπληξία. Οι ασθενείς με καρδιακή ανακοπή είναι επηρρεπείς σε νοσοκομειακές λοιμώξεις, οι οποίες συμβάλλουν στη μετά την αναζωογώνηση θνησιμότητα. Υποθέσαμε ότι στρες-δόση στεροειδών κατά τη διάρκεια και/ή μετά την ανάταξη μπορεί να συσχετίζεται με μειωμένο κίνδυνο θανάτου εξ αιτίας μετά της ανακοπής λοιμώξεων που οδηγούν σε σηπτική καταπληξία. Μέθοδοι: Διεξάγαμε μια επανανάλυση [cumulative incidence competing risks (CICR)] στοιχείων από 2 προηγούμενες, τυχαιοποιημένες κλινικές μελέτες. Οι μελέτες αυτές αξιολογούσαν τη βαζοπρεσσίνη, τα στεροειδή και την επινεφρίνη [vasopressin, steroids, and epinephrine (VSE)] κατά τη διάρκεια της αναζωογώνησης και τη στρες-δόση στεροειδών μετά την αναζωογώνηση σε ασθενείς που είχαν υποστεί ενδονοσοκομειακή ανακοπή. Στις πρωτογενείς αναλύσεις, οι ασθενείς με μετά την ανάταξη καταπληξία χωρίστηκαν σε μια ομάδα που έλαβε Στεροειδή (n=118) ή στην ομάδα Μη Στεροειδή (n=73) , σύμφωνα με την αρχή «as treated». Εφαρμόσαμε CICR Cox ανάλυση παλινδρόμησης ώστε να καθορίσουμε σχετικές με την αιτία αναλογίες κινδύνου [cause-specific hazard ratios (CSHRs)] για προκαθορισμένους προγνωστικούς παράγοντες μοιραίας σηπτικής καταπληξίας (πρωτογενής έκβαση), θάνατο από μη λοιμώδη αίτια και πτωχή ενδονοσοκομειακή έκβαση outcome (cerebral performance category score ≥3). Στις αναλύσεις ευαισθησίας, τα δεδομένα επεξεργάστηκαν σύμφωνα με την αρχή intention-to-treat (ITT) (ομάδα VSE, n=103; Ομάδα ελέγχου, n=88). Αποτελέσματα: Η μοιραία σηπτική καταπληξία ήταν λιγότερο πιθανή στην ομάδα Στεροειδή έναντι στην ομάδα Μη Στεροειδή [CSHR, 0.40, 95% confidence interval (CI), 0.20-0.82; p=0.012]. Ο θάνατος από μη λοιμώδη αίτια και η πτωχή ενδονοσοκομειακή έκβαση προβλέφθηκαν από την ομάδα και από τη σχετιζόμενη με την αναζωογώνηση δόση διττανθρακικών. Τα αποτελέσματα της ανάλυσης ΙΤΤ για τη μοιραία σηπτική καταπληξία και την πτωχή ενδονοσοκομειακή έκβαση ήταν παρόμοια. Η ομάδα Στεροειδή σε σχέση με την ομάδα ΜηΣτεροειδή είχε περισσότερες ημέρες ελεύθερες οργανικής ανεπάρκειας και εκτός αναπνευστήρα, καθώς και χωρίς επεισόδια υπεργλυκαιμίας/ χρήσης ινσουλίνης. Συμπέρασμα: Σε αυτήν την επανανάλυση, η στρες-δόση στεροειδών συσχετίστηκε με χαμηλότερο κίνδυνο μετά την αναζωογώνηση μοιραίας σηπτικής καταπληξίας. Η απόδειξη της αιτιότητας απαιτεί επιβεβαιώση από μελλοντικές τυχαιοποιημένες μελέτες.

A DYNAMIC COMPETING RISKS MODEL

1999 ◽  
Vol 13 (3) ◽  
pp. 333-358 ◽  
Author(s):  
Marcus A. Agustin ◽  
Edsel A. Peña
Keyword(s):  
Competing Risks ◽  
Failure Rate ◽  
System Reliability ◽  
Completion Time ◽  
Failure Time ◽  
Asymptotic Properties ◽  
Task Completion ◽  
Series System ◽  
Component Failure ◽  
Testing Period

We consider a series system with p components where the failure rate of each component depends on the residual number of defects present. Successive tasks are given to the system with each task completion time independent of each component failure time. Based on the outcomes over a fixed testing period, the asymptotic properties of the estimators of the component parameters, task completion parameters, and eventual system reliability are obtained.

Development of apical pits in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water

1983 ◽  
Vol 41 ◽  
pp. 462-463
Author(s):  
Richard L. Leino ◽  
Jon G. Anderson ◽  
J. Howard McCormick
Keyword(s):  
Confidence Interval ◽  
Chronic Exposure ◽  
Lake Superior ◽  
Pimephales Promelas ◽  
Chloride Cells ◽  
Fathead Minnows ◽  
Secondary Lamellae ◽  
Untreated Water ◽  
Water Ph ◽  
Flow Through

Groups of 12 fathead minnows were exposed for 129 days to Lake Superior water acidified (pH 5.0, 5.5, 6.0 or 6.5) with reagent grade H2SO4 by means of a multichannel toxicant system for flow-through bioassays. Untreated water (pH 7.5) had the following properties: hardness 45.3 ± 0.3 (95% confidence interval) mg/1 as CaCO3; alkalinity 42.6 ± 0.2 mg/1; Cl- 0.03 meq/1; Na+ 0.05 meq/1; K+ 0.01 meq/1; Ca2+ 0.68 meq/1; Mg2+ 0.26 meq/1; dissolved O2 5.8 ± 0.3 mg/1; free CO2 3.2 ± 0.4 mg/1; T= 24.3 ± 0.1°C. The 1st, 2nd and 3rd gills were subsequently processed for LM (methacrylate), TEM and SEM respectively.Three changes involving chloride cells were correlated with increasing acidity: 1) the appearance of apical pits (figs. 2,5 as compared to figs. 1, 3,4) in chloride cells (about 22% of the chloride cells had pits at pH 5.0); 2) increases in their numbers and 3) increases in the % of these cells in the epithelium of the secondary lamellae.

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