Showing papers on "Reliability (statistics) published in 1988"

Measuring the accuracy of diagnostic systems

Abstract: Diagnostic systems of several kinds are used to distinguish between two classes of events, essentially "signals" and "noise". For them, analysis in terms of the "relative operating characteristic" of signal detection theory provides a precise and valid measure of diagnostic accuracy. It is the only measure available that is uninfluenced by decision biases and prior probabilities, and it places the performances of diverse systems on a common, easily interpreted scale. Representative values of this measure are reported here for systems in medical imaging, materials testing, weather forecasting, information retrieval, polygraph lie detection, and aptitude testing. Though the measure itself is sound, the values obtained from tests of diagnostic systems often require qualification because the test data on which they are based are of unsure quality. A common set of problems in testing is faced in all fields. How well these problems are handled, or can be handled in a given field, determines the degree of confidence that can be placed in a measured value of accuracy. Some fields fare much better than others.

Reliability of a timeline method: assessing normal drinkers' reports of recent drinking and a comparative evaluation across several populations.

Abstract: Summary Since alcohol research involves both clinical and non-clinical populations, it is important to evaluate drinking assessment methods across different subject populations. Over the past several years, the reliability of the timeline (TL) method of gathering retrospective reports of recent drinking has been evaluated in several studies, and this method has been shown to have generally high reliability with outpatient alcohol abusers, in-patient chronic alcoholics, and normal drinker college students. The present study examined the reliability of the TL method with normal drinkers in the general population. Similar to other populations, the test-retest reliability of male (n=31) and female (n=31) normal drinkers' reports of recent drinking behaviour was found to be generally high. Data gathered by the TL method were also compared to data gathered from the same subjects using a common quantity-frequency (QF) method. Consistent with earlier reports, QF categorization provided a relatively insensitive measure of individual differences in drinking behaviour as compared to TL-derived data. Since the TL method has now been shown to have fairly good reliability for assessing recent drinking across a broad range of drinkers, it can be used for comparative evaluations of drinking behaviour across studies with different subject populations.

Water Distribution Reliability: Simulation Methods

Abstract: Following a companion paper on analytical methods, this paper presents simulation as a complementary method for analyzing the reliability of water distribution networks. For this simulation, the distribution system is modeled as a network whose pipes and pumps are subject to failure. Nodes are targeted to receive a given supply at a given head. If this head is not attainable, supply at the node is reduced. Pumps and pipes fail randomly, according to probability distributions with user‐specified parameters. Several reliability measures are estimated with this simulation. Confidence intervals are also supplied for some of these reliability measures. Simulation results are presented for a small network (ten nodes) and a larger network (sixteen nodes). Simulation enables computation of a much broader class of reliability measures than do analytical methods, but it requires considerably more computer time and its results are less easy to generalize. It is therefore recommended that analytical and simulation me...

Distributed programming in Argus

Abstract: Argus—a programming language and system developed to support the implementation and execution of distributed programs—provides mechanisms that help programmers cope with the special problems that arise in distributed programs, such as network partitions and crashes of remote nodes.

Microelectronics reliability

Abstract: The author points out the importance of the involvement of the design and manufacturing team in achieving reliability of microelectronic devices. A method of verifying reliability goals through calculation of failure rates based on life test parameters is described. An example illustrating the method is shown. >

Reliability Assessment of Large Electric Power Systems

Abstract: This book covers a wide range of relevant material related to present-day knowledge and application in power system reliability. Increasing socioeconomic pressures to create safe and reliable power systems are being exerted on utilities by government, environmental groups and society in general. The material presented in this book will play a role in finding acceptable solutions to such pressures and will encourage the increased use of reliability techniques in practical applications.

Validity and Reliability of Self Report Measures of Physical Activity: An Information-Processing Perspective

Abstract: The published data on the reliability of self report measures of physical activity most commonly used in the cardiovascular disease epidemiology literature revealed high test-retest reliability coefficients for two of the measures, and modest to nonexistent intertest correlations Validity coefficients were low to modest The published data on the accuracy of the self report measures, however, revealed memory decay, memory of rare events alone, and lack of motivation in memory recall An information processing model, composed of encoding, storage, and retrieval processes is proposed to understand the memory of physical activity, and to identify necessary skills for accurate self report identified at each step in the process Questions requiring further research to specify this model and, in turn, improve accuracy of recall, are raised

Improvement Of Second‐Order Reliability Estimates by Importance Sampling

Abstract: The calculation of probability integrals is one of the most important tasks in structural reliability. First-order and asymptotic second-order methods have been proposed. The method of importance sampling is applied to determine the remaining error and to define a correction factor for the asymptotic second-order methods. The method can be made arbitrarily exact at the expense of more numerical effort.

Reliability and Validity in Field Research: Some Strategies and Tactics

Abstract: This article is concerned with issues of validity and reliability in field research. It examines the nature of, and threats to validity and reliability in field studies and documents some strategies and tactics that may be employed to counter those threats. At a time when field research is becoming an increasingly important and necessary method for more accounting researchers, it is hoped that an article such as this may provide useful reference for the conduct, communication and evaluation of field research in accounting.

Probability Integration by Directional Simulation

Abstract: Reliability evaluation methods based on directional simulation for structural reliability analysis is treated herein. The methods can be used to check results obtained by a first‐ or second‐order reliability method. Directional importance sampling based on first‐ and second‐order reliability results is used to reduce the variance on the probability estimator. Sampling densities and procedures for important types of failure surfaces considered in the space of independent and standardized Gaussian variables are set up. The types include hyper‐spheres, hyperplanes, rotationally symmetrical hyperparaboloids, surfaces defining a convex polyhedral failure set, as well as series‐systems failure surfaces.

Validity and reliability of the Chinese Hamilton Depression Rating Scale.

Abstract: The reliability and validity of the Chinese version of the 17-item Hamilton Depression Rating Scale (CHDS) was assessed. Interrater reliability was excellent, the item total-score correlations were good, and the internal reliability was satisfactory. The concurrent validity was tested by correlating the CHDS score with the Global Assessment Scale score; the strong negative correlation found indicated that the CHDS reflects the overall level of disability. Five distinct factors were generated by principle-component analysis; these factors account for 52.4% of the total variance. Rigorous evaluation of the numerous translated scales being used in clinical and research settings of non-Western countries is important.

Parameter Estimation in Reliability and Life Span Models

Abstract: Offers an applications-oriented treatment of parameter estimation from both complete and censored samples; contains notations, simplified formats for estimates, graphical techniques, and numerous tables and charts allowing users to calculate estimates and analyze sample data quickly and easily. Anno

Water Distribution Reliability: Analytical Methods

Abstract: Probabilistic reliability measures for the performance of water distribution networks are developed and analytical methods for their computation explained. The paper begins with a review of reliability considerations and measures for water supply systems, making use of similar notions in other fields. It classifies reliability analyses according to the level of detail with which the water system is modeled, and then concentrates on methods relevant to networks. Two probabilistic measures, reachability and connectivity, are explored for use in water distribution systems. Two algorithms for their computation are presented, one for series-parallel networks and one for general networks. These measures are computed for two systems, each with ten nodes. Additionally, the probability that a given point receives sufficient supply is proposed for use as a reliability measure. An algorithm is presented for the calculation of this measure, which combines a capacitated network algorithm with a method to efficiently search through network configurations involving multiple link failures. This measure is calculated for the two sample systems.

A review of the methods for the measurement of coating-substrate adhesion☆

Abstract: Modern coating techniques now offer the possibility of modifying the surface of an engineering component to achieve improvements in both performance and reliability. One important and often overriding factor is the degree of adhesion between the coating and its substrate, and the aim of this paper is to discuss the methods which can be used to assess this critical property of the coating-substrate system. The advantages and disadvantages of each technique, e.g. the pressure-sensitive tape test, indentation testing, the scratch test, laser methods etc., are reviewed.

A comparison of algorithms for terminal-pair reliability

Abstract: Four algorithms for the terminal-pair-reliability problem are compared. Nelson (1970), Lin (1976), Shooman (1968), and Dotson (1979) algorithms are used in this study. It is shown that the Dotson algorithm is the fastest among the terminal-pair reliability algorithms analyzed. The Dotson algorithm is suited not only for numerical reliability, but for obtaining symbolic expression for the terminal-pair reliability with no additional effort. By modifying the Dotson algorithm the efficiency can be further improved. The modifications to this algorithm are listed and the reliability of the modified Dotson algorithm is computed. >

3 Stress-strength models for reliability

Abstract: Publisher Summary When ascertaining the reliability of equipment or the viability of a material, it is also necessary to take into account the stress conditions of the operating environment. That is, uncertainty about the actual environmental stress to be encountered should be modeled as random. The terminology stress-strength model makes explicit that both stress and strength are treated as random variables. In the simplest stress-strength model, X is the stress placed on the unit by the operating environment and Y is the strength of the unit. A unit is able to perform its intended function if its strength is greater than the stress imposed upon it. Reliability is defined as the probability that the unit is strong enough to overcome the stress. This model has found an increasing number of applications in civil, mechanical, and aerospace engineering. The chapter discusses the nonparametric inference about stress–strength reliability, nonparametric inference about stress–strength reliability, the normal and the Weibull stress–strength models, extensions of the basic stress–strength model, and Bayesian inference procedures.

Human reliability analysis

Abstract: The authors present a treatment of human reliability analysis incorporating an introduction to probabilistic risk assessment for nuclear power generating stations. They treat the subject according to the framework established for general systems theory. Draws upon reliability analysis, psychology, human factors engineering, and statistics, integrating elements of these fields within a systems framework. Provides a history of human reliability analysis, and includes examples of the application of the systems approach.

Conjoint Analysis Reliability: Empirical Findings

Abstract: This paper looks at the comparative reliability of different methodological variants of the conjoint analysis procedure. It differs from previous studies in that it looks at three methods of data collection Full Profile, Trade-off Matrices, and Paired Comparison and two levels of a key attribute price across five different product categories. In addition it tests these manipulations using two different reliability assessment procedures. The results show that most manipulations have a significant effect on the reliability scores and many interaction terms are significant.

Bayesian reliability analysis of series systems of binomial subsystems and components

Abstract: A Bayesian procedure is presented for estimating the reliability of a series system of independent binomial subsystems and components. The method considers either test or prior data (perhaps both or neither) at the system, subsystem, and component level. Beta prior distributions are assumed throughout. Inconsistent prior judgments are averaged within the simple-to-use procedure. The method is motivated by the following practical problem. It is required to estimate the overall reliability of a certain air-to-air heat-seeking missile system containing five major subsystems with up to nine components per subsystem. The posterior distribution of the overall missile-system reliability from which the required estimates are obtained is computed.

Reliability improvement and economic benefits of on-line monitoring systems for large induction machines

Abstract: Microprocessor-based monitoring systems are being developed for the regular analysis of large induction machine variables and to predict possible fault conditions, so that preventive maintenance can be organized in a cost-effective manner. A method for the evaluation of the improvement of machine reliability made by such monitoring systems is presented. An economic and financial analysis to examine the viability of a condition monitoring system for a large machine using comprehensive rotor, stator, and other parameter measurements is developed. In two case studies, the costs of design, construction, mounting, and operation of condition monitoring systems are discussed, and estimates are made at current costs. These costs are balanced against the costs avoided in cases of unexpected machine failures, lost production, and repairs. Cost estimates for repairs and downtime are made using published information from previous reliability surveys on electrical machines. Information is presented for different machine sizes, which will indicate any relevance of the machine size when evaluating monitoring systems. >

Assessing student approaches to learning

Abstract: The Learning Process Questionnaire (LPQ) and the Study Process Questionnaire (SPQ) are designed to assess the more important motives. strategies and approaches to learning of secondary and tertiary students. respectively. An approach to learning. in line with a metacognitively based theory of student learning is defined as a particular motive for learning that is associated with a congruent strategy. Three such approaches surface, deep, and achieving and one composite approach, deep-achieving, represent the most important ways in which students consistently approach academic tasks. Norms for each subscale and scale score arc available in deciles, separately for males and females, and in the case of the LPQ, for middle and senior high school, and in that of the SPQ. for CAE and university and for the faculties of arts, education, and science. Some data on the sampling, reliability, and validity are provided, and the use of the instruments in teaching, counseling, and research is discussed briefly.

Retaining qualitative validity while gaining quantitative reliability and validity: development of the Transition to Parenthood Concerns Scale

Abstract: This article raises issues about the retention of qualitative validity while establishing psychometric estimates of reliability and validity for a scale that was developed from inductively generated concepts to assess and evaluate the learning needs and concerns of expectant parents in the trimester before their baby's birth. A set of practical procedures for pilot testing qualitatively based scales is described. The three procedures, which provide estimates of clarity, apparent internal consistency, and content validity, preserve the assumptions underlying qualitative methods. The ratings from these procedures have provided a base for item and scale revisions and formal quantitative testing.

The reliability of the family history method for psychiatric diagnoses

Abstract: • We evaluated the test-retest interrater reliability of the Family History Research Diagnostic Criteria (FH-RDC) in 58 depressed patients who described 341 first-degree relatives. Reliability was examined as a function of the threshold to determine caseness. In general, diagnostic reliability was good-excellent for specific FH-RDC disorders, but not for the residual category of other psychiatric disorder. A higher diagnostic threshold was associated with greater reliability, especially for the diagnosis of depression. Patient variance accounted for a greater percentage of the disagreements between the acthan did rater variance.