Showing papers on "Reliability (statistics) published in 1996"

Structural Reliability Methods

Abstract: Partial Safety Factor Method Probabilistic Information Simple Reliability Index Geometric Reliability Index Generalized Reliability Index Transformation Sensitivity Analysis Monte Carlo Methods Load Combinations Statistical and Model Uncertainty Decision Philosophy Reliability of Existing Structures System Reliability Analysis Introduction to Process Descriptions.

An Introduction to Reliability and Maintainability Engineering

Abstract: 1 IntroductionI Basic Reliability Models2 The Failure Distribution3 Constant Failure Rate Model4 Time-Dependent Failure Models5 Reliability of Systems6 State Dependent Systems7 Physical Reliability Models8 Design for Reliability9 Maintainability10 Design for Maintainability11 AvailabilityII The Analysis of Failure Data12 Data Collection and Empirical Methods13 Reliability Testing14 Reliability Growth Testing15 Identifying Failure and Repair Distributions16 Goodness-of-Fit TestsIII Application17 Reliability Estimation and Application18 Implementation

Unified Huntington's disease rating scale: reliability and consistency

Abstract: ! The Unified Huntington’s Disease Rating Scale (UHDRS) was developed as a clinical rating scale to assess four domains of clinical performance and capacity in HD: motor function, cognitive function, behavioral abnormalities, and functional capacity. We assessed the internal consistency and the intercorrelations for the four domains and examined changes in ratings over time. We also performed an interrater reliability study of the motor assessment. We found there was a high degree of internal consistency within each of the domains of the UHDRS and that there were significant intercorrelations between the domains of the UHDRS, with the exception of the total behavioral score. There was an excellent degree of interrater reliability for the motor scores. Our limited longitudinal database indicates that the UHDRS may be useful for tracking changes in the clinical features of HD over time. The UHDRS assesses relevant clinical features of HD and appears to be appropriate for repeated administration during clinical studies.\

System reliability theory : models and statistical methods

Abstract: Failure Models. Qualitative System Analysis. Systems of Independent Components. Component Importance. Markov Models. Counting Processes. Dependent Failures. Life Data Analysis. Accelerated Life Testing. Bayesian Reliability Analysis. Reliability Data Sources. Appendices. References. Indexes.

IBM experiments in soft fails in computer electronics (1978–1994)

Abstract: This review paper has described the experimental work at IBM over the last fifteen years in evaluating the effect of cosmic rays on terrestrial electronic components. This work originated in 1978, went through several years of research to verify its magnitude, and became a significant factor in IBM`s efforts toward improved product reliability.

A test system for teaching overall power system reliability assessment

Abstract: This paper presents the concept of overall power system reliability evaluation using an educational test system. The paper extends an existing test system by developing the necessary distribution and subtransmission networks. The extended test system has all the main facilities, such as generation, switching stations, transmission, sub-transmission and radial distribution networks found in a practical system. The test system, is however, sufficiently small that students can analyze it using hand calculations or by developing small computer programs to fully understand the reliability models and evaluation techniques. Overall power system reliability evaluation is concerned with providing acceptable customer service. This is an important concern in today's electric utility environment. This should therefore be an essential element in teaching power system reliability evaluation at either the graduate or undergraduate level, The extended test system presented in this paper and the concepts presented assist in satisfying this requirement.

User-friendly software for Mössbauer spectrum analysis

Abstract: A new user-friendly software for analysis of Mossbauer-spectra has been developed. The program makes use of the advantages provided by the current generation of fast personal computers. An Evolution Algorithm1,2 is used for global search of Mossbauer parameters in order to enhance the reliability of the obtained results. Fitting of Lorentzians, Pseudo-Voigt line profiles, and deriving hyperfine-field distributions including correlations and combinations and Mossbauer Line Sharpening by Fourier transformation provide a wide range of applicability.

Construction and validation of a quality of life questionnaire in chronic lower limb venous insufficiency (CIVIQ)

Abstract: Quality of life may be considerably reduced in patients who are suffering from chronic lower limb venous insufficiency, although existing generic quality of life instruments (NHP, SF-36 or SIP) cannot completely identify their specific complaints. The Chronic Venous Insufficiency Questionnaire (CIVIQ) has been developed by iterative process. First, a pilot group of 20 patients was used to identify a number of important features of quality of life affected by venous insufficiency, other than physical symptoms of discomfort. A second study involving 2,001 subjects was used to reduce the number of items. Subjects were asked to score both the severity of their problems and the importance they attributed to each problem on a 5-point Likert scale. The importance items found in patients with venous insufficiency were subjected to factorial analyses (PCA, PAF). The final version is a 20-item self-administered questionnaire which explores four dimensions: psychological, physical and social functioning and pain. Internal consistency of the questionnaire was validated for each dimension (Cronbach's alpha > 0.820 for three out of four factors). Reproducibility was confirmed in a 60 patient test-retest study. Pearson's correlation coefficients for both the four dimension subscales and for the global score at 2-week intervals were greater than 0.940. Finally, the questionnaire was tested in a randomized clinical trial of 934 patients in order to assess responsiveness and the convergent validity of the instrument, together with the patient's own quality of life. This study demonstrated that convergence was valid: Pearson's correlation coefficients between clinical score differences and quality of life score differences were small (from 0.199–0.564) but were statistically different from 0 (p 0.80). Reliability, face, content, construct validity and responsiveness were also determined for this specific quality of life questionnaire relating to venous insufficiency. Results suggest that this questionnaire may be used with confidence to assess quality of life in clinical trials on chronic venous insufficiency.

How Retirement Saving Programs Increase Saving

Abstract: This paper summarizes the authors work on the effect of IRA and 401(k) contributions on net personal saving. They consider many different nonparametric approaches to controlling for heterogeneity in individual saving behavior and conclude that the weight of the available evidence suggests that contributions to both IRAs and 401(k)s largely represent new saving. The authors devote particular attention to reconciling their results with the findings in other studies that reach different conclusions, sometimes using the same databases that the authors analyze. Methodological limitations that undermine the reliability of results in other studies explain many of these disparities.

Performance and Reliability Analysis of Computer Systems

Abstract: Table of

Estimating the Reliability of a Single-Item Measure:

Abstract: Single-item measures of employees' attitudes and beliefs are generally discouraged because their (internal consistency) reliability cannot be estimated. This results in the concern that reliability may be unacceptably low, particularly when compared to scales used to measure the same construct. A method for estimating the reliability of a single-item measure is demonstrated on original data that included both a single-item and a multiple-item measure of three constructs, namely, Over-all Job Satisfaction, Perceived Amount of Participation, and Desired Amount of Participation in decision-making. The average minimum estimated reliability for these single-item measures is .57; however, a realistic yet conservative estimate of their likely minimum reliability is at least .70.

A survey and taxonomy of strategy‐related performance measures for manufacturing

Abstract: Although the topic of manufacturing performance measurement has recently attracted considerable interest, little has been done to enumerate or classify the measures that exist. Lists 125 different strategy‐related measures that were found through a survey of accounting, manufacturing and managerial literature. Develops a taxonomy which categorizes those measures according to competitive priority (cost, quality, flexibility, delivery reliability, or speed), data source (internal or external), data type (objective or subjective), measure reference (self‐referenced or benchmark), and process orientation (process input or process outcome). Finds that the largest number of measures have been proposed for the competitive priority of flexibility and the fewest for delivery reliability. Most measures have focused only on process outcomes using self‐referenced objective data from internal sources. Based on these results, suggests that companies and academic researchers utilize new or different measures to assess adequately strategy‐related manufacturing performance.

New developments in the use of measures of honesty integrity, conscientiousness, dependability trustworthiness, and reliability for personnel selection

Abstract: This paper is the fourth in a series of reviews of the use of measures of honesty, integrity, conscientiousness, dependability, trustworthiness, and reliability for personnel selection (see Sackett & Decker, 1979; Sackett & Harris, 1984; Sackett, Burris, & Callahan, 1989). New developments reviewed include an examination of professional and congressional inquiry into this area of testing, rapid growth of the validity data base, new insight into similarities and differences between different tests, and links to the Big Five personality dimensions. Inquiries into relationships with other constructs, including cognitive ability, moral reasoning, and social desirability are reviewed, as are applicant reactions to these tests. The effects of the Civil Rights Act of 1991 and the Americans with Disabilities Act are considered.

Engineering multiversion neural-net systems

Abstract: In this paper we address the problem of constructing reliable neural-net implementations, given the assumption that any particular implementation will not be totally correct. The approach taken in this paper is to organize the inevitable errors so as to minimize their impact in the context of a multiversion system, i.e., the system functionality is reproduced in multiple versions, which together will constitute the neural-net system. The unique characteristics of neural computing are exploited in order to engineer reliable systems in the form of diverse, multiversion systems that are used together with a "decision strategy" (such as majority vote). Theoretical notions of "methodological diversity" contributing to the improvement of system performance are implemented and tested. An important aspect of the engineering of an optimal system is to overproduce the components and then choose an optimal subset. Three general techniques for choosing final system components are implemented and evaluated. Several different approaches to the effective engineering of complex multiversion systems designs are realized and evaluated to determine overall reliability as well as reliability of the overall system in comparison to the lesser reliability of component substructures.

Sampling Error and Selecting Intercoder Reliability Samples for Nominal Content Categories

Abstract: This study views intercoder reliability as a sampling problem. It develops a formula for generating sample sizes needed to have valid reliability estimates. It also suggests steps for reporting rel...

Industry experience with special protection schemes

Abstract: Special protection schemes are those designed to detect one or more predetermined system conditions that have a high probability of causing unusual stress on the power system, and for which preplanned remedial action is considered necessary The failure of these schemes to accurately detect the defined conditions, or their failure to carry out the required preplanned remedial action, can lead to very serious and costly power system disturbances It is natural, therefore, that a concern for the reliability of these schemes has been expressed This paper reports on a joint IEEE-CIGRE survey to determine the experience with special protection schemes, and to question the designers and operators of these schemes regarding the reliability of performance Questions were also directed to the design process itself, the reliability criteria used for the design, and the analytical methods used to assure reliability in the design

Comparison of Methods for Predicting Deficient-Network Performance

Abstract: When a nodal demand is excessive as in a fire-flow condition or when a pump fails or a pipe breaks, a water distribution system (WDS) may temporarily become deficient and unable to satisfy all nodal demands. However, the prediction of the performance of a WDS under a temporarily-deficient condition is necessary for simulation-based reliability analysis and design of WDSs. Available methods for such prediction are reviewed herein. When the actual outlets are considered as demand nodes the methods which simultaneously consider the nodal flows and heads give fairly accurate and similar results. However, when the demands of secondary networks are assumed concentrated at the nodes of the primary WDSs, the prediction of the deficient-condition performance of a primary WDS is rather approximate. For reliability purposes, however, the method using parabolic head-discharge relationship (no flow at minimum head to required flow at desirable head), is the best for prediction of deficient-network performance.

Are Simple Gain Scores Obsolete

Abstract: It is widely believed that measures of gain, growth, or change, expressed as simple differences between pretest and posttest scores, are inherently unreliable It is also believed that gain scores lack predictive validity with respect to other criteria However, these conclu sions are based on misleading assumptions about the values of parameters in familiar equations in classical test theory The present paper examines modified equa tions for the validity and reliability of difference scores that describe applied testing situations more realisti cally and reveal that simple gain scores can be more useful in research than commonly believed

Reducing Distance Dependent Errors for Real-Time Precise DGPS Applications by Establishing Reference Station Networks

Abstract: Distance dependent errors limit the accuracy of high precision real-time DPGS applications to 1 to 10 ppm. The objective of this investigation is to improve the reliability and speed of On-The-Way (OTW) ambiguity resolution and to enhance the accuracy of the GPS solution by using data from multiple reference stations. Extensive test measurements carried out in the northern part of Germany using the real-time processing software package GNRT with only one reference station clearly show distant dependent errors of about 1 ppm and more. The postprocessing simulation of a reference station network reduces the effects to generally less than 1 cm without any distance dependencies.

Reliability and Validity of the Pediatric Evaluation of Disability Inventory

Abstract: The reliability and validity of the Pediatric Evaluation of Disability Inventory (PEDI) were investigated in a series of three studies: 1) intrarater reliability (n = 23), 2) interrespondent reliability (n = 1 7), and 3) concurrent validity with the Peabody Developmental Motor Scales (PDMS) (n = 25)

The Utility of Isokinetic Dynamometry in the Assessment of Human Muscle Function

Abstract: Isokinetic dynamometry has become a favoured method for the assessment of dynamic muscle function in both clinical research and sports environments. Several indices, such as peak torque, are used in the literature to characterise individual, group or larger population performance via these sophisticated data acquisition systems. Research suggests that there are several competing demands on the design of the measurement protocol which may affect the measurement of isokinetic strength and subsequent suitability of data for meaningful evaluation and interpretation. There is a need to increase measurement rigour, reliability and sensitivity to a level which is commensurate with the intended application, via more elaborate multiple-trial protocols. However, this may be confounded by logistical and financial constraints or reduced individual compliance. The net effect of the interaction of such demands may be considered to be the utility of the isokinetic dynamometry protocol. Of the factors which impinge on utility, those which relate to reliability afford the most control by the test administrator. Research data suggest that in many measurement applications, the reliability and sensitivity associated with all frequently-used indices of isokinetic leg strength which are estimated via single-trial protocols, are not sufficient to differentiate either performance change within the same individual or between individuals within a homogeneous group. While such limitation may be addressed by the use of protocols based on 3 to 4 inter-day trials for the index of peak torque, other indices which demonstrate reduced reliability, for example the composite index of the ratio of knee flexion to extension peak torque, may require many more replicates to achieve the same level of sensitivity. Here, the measurement utility of the index may not be sufficient to justify its proper deployment.

Engineering Reliability: Fundamentals and Applications

Abstract: 1. Introduction and Overview. 2. Probability and Random Variables. 3. Catastrophic Failure Models and Reliability Functions. 4. Probability Distribution Functions and Their Application in Reliability Evaluation. 5. Combinatorial Aspects of System Reliability. 6. Markov Models. 7. Reliability Evaluation of Engineering Systems Using Markov Models. 8. Approximate Methods. 9. Reliability and Economics. 10. Accelerated Testing and Models. Appendix A: Matrix Fundamentals. Appendix B: Boolean Algebra. Appendix C: The Laplace Transform. Appendix D: Differential Equations. Appendix E: Some Useful Derivatives and Integrals. Appendix F: The Beta Function. Appendix G: The Gamma Function. Appendix H: Tables of Values of Factorial n. Appendix I: Binomial Coefficients. Appendix J: Tables of Values of Exponential Functions. Appendix K: Standard Normal Curve Areas. Appendix L: Standard Normal Curve Ordinates. References. Answers to Problems. Index.