Showing papers on "Reliability (statistics) published in 1991"

A reliability test system for educational purposes-basic distribution system data and results

Abstract: A description is presented of an electrical distribution system for use in teaching power system reliability evaluation. It includes all the main elements found in practical systems. However, it is sufficiently small that students can analyze it using hand calculations and hence fully understand reliability models and evaluations techniques. All the data needed to perform basic reliability analyses are included in this work. It also contains the basic results for a range of case studies and alternative design/operating configurations. >

Experimental analysis of choice

Abstract: Experimental choice analysis continues to attract academic and applied attention. We review what is known about the design, conduct, analysis, and use of data from choice experiments, and indicate gaps in current knowledge that should be addressed in future research. Design strategies consistent with probabilistic models of choice process and the parallels between choice experiments and real markets are considered. Additionally, we address the issues of reliability and validity. Progress has been made in accounting for differences in reliability, but more research is needed to determine which experiments and response procedures will consistently produce more reliable data for various problems.

Reliability engineering handbook

Abstract: This volume, the second of two devoted to the subject, covers the range of reliability engineering, from product and system design through manufacturing, implementation and maintenance. Illustrated with practical examples, the books show how to specify components, equipment and system reliability - and how to implement these requirements. Comprehensive and easy to understand, these books demonstrate how to analyze time-to-failure data from components, systems and equipment to obtain their distribution, reliability, failure rate and mean lifespan; provide theoretical and practical tools for designing, testing and implementing the probability and capacity of parts, components, equipment, products and systems performance; and include applications to purchasing, engineering, research, development, manufacturing and quality control.

The Reliability of Survey Attitude Measurement: The Influence of Question and Respondent Attributes

Abstract: Several theoretical hypotheses are developed concerning the relation of question and respondent characteristics to the reliability of survey attitude measurement. To test these hypotheses, reliabil...

Measurement and Reliability: Statistical Thinking Considerations

Abstract: Reliability is defined as the degree to which multiple assessments of a subject agree (reproducibility). There is increasing awareness among researchers that the two most appropriate measures of reliability are the intraclass correlation coefficient and kappa. However, unacceptable statistical measures of reliability such as chi-square, percent agreement, product moment correlation, as well as any measure of association and Yule's Y still appear in the literature. There are costs associated with improper measurements, unreliable diagnostic systems, inappropriate statistics and measures of reliability, and poor quality research. Costs are incurred when misleading information directs resources and talents into nonproductive avenues of research. The consequences of unreliable measurements and diagnosis are illustrated with some studies of schizophrenia.

Psychometric evaluation of an after-scenario questionnaire for computer usability studies: the ASQ

Abstract: A three-item after-scenario questionnaire was used in three related usability tests in different areas of the United States. The studies had eight scenarios in common. After participants finished a scenario, they completed the After-Scenario Questionnaire (the ASQ). A factor analysis of the responses to the ASQ items revealed that an eight-factor solution explained 94 percent of the variability of the 24 (eight scenarios by three items per scenario) items. The varimax-rotated factor pattern showed that these eight factors were clearly associated with the eight scenarios. The benefit of this research to system designers is that this three-item questionnaire has acceptable psychometric properties of reliability, sensitivity, and concurrent validity, and may be used with confidence in other, similar usability studies.

A Comparison of Four Computer Attitude Scales

Abstract: Ninety-eight student teachers enrolled in an introductory computer course were simultaneously administered four computer attitude scales. The responses were used to compare the reliability, dimensi...

Statistical analysis of reliability data

Abstract: Statistical Concepts in Reliability. Probability Distributions in Reliability. Statistical Methods for Single Samples. Regression Models for Reliability Data. Proportional Hazards Modelling. The Bayesian Approach. Multivariate Models. Repairable Systems. Discussion Models for Systems Reliability. Appendix. References. Indices.

Test-retest Reliability of the Hearing Handicap Inventory for Adults

Abstract: The test-retest reliability of the Hearing Handicap Inventory for Adults (HHIA) was assessed on a sample of 28 hearing-impaired adults. Reliability estimates were obtained to set the stage for using the HHIA as an outcome measure in aural rehabilitation. The test-retest reliability was quite

Finite Element Reliability of Geometrically Nonlinear Uncertain Structures

Abstract: A general framework for finite element reliability analysis based on the first‐ and second‐order reliability methods, FORM and SORM, is presented. New expressions for the required gradients of the response of geometrically nonlinear structures are derived and implemented in an existing finite element code, which is then merged with a FORM/SORM reliability code. The gradient computation does not require repeated solutions of the nonlinear response and is free of the errors inherent in the perturbation method. The proposed reliability method offers significant advantages over the conventional Monte Carlo simulation approach. The method is illustrated for a plate problem with random field properties, random geometry, and subjected to random static loads. The example represents the first application of the finite element method in conjunction with SORM, for a system reliability problem, and involving non‐Gaussian random fields. Extensive analyses of reliability sensitivities with respect to parameters definin...

UV light-permeable glass and article comprising the same

Abstract: A UV light-permeable optical glass consisting of a fluorine-doped synthetic quartz glass, which has a long term reliability.

On the reliability of testlet‐based tests

Abstract: If a test is constructed of testlets one must take into account the within-testlet structure in the calculation of test statistics Failing to do so may yield serious biases in the estimation of such statistics as reliability In this paper we demonstrate how to calculate the reliability of a testlet-based test We show that traditional reliabilities calculated on two reading comprehension tests constructed of four testlets are substantial overestimates

Test‐Retest Reliability of the End‐User Computing Satisfaction Instrument

Abstract: The development of reliable and valid measures of user-information satisfaction is becoming increasingly important to both practitioners and researchers. Measures of reliability include internal consistency and stability. Recent research has raised concerns about the stability of user information satisfaction measures. Using the test-retest correlation method, this article assesses short- and long-range stability of a 12-item scale for measuring end-user computing satisfaction. It examines the stability of individual items and subscales as well as the 12-item instrument. The results suggest that the instrument is internally consistent and stable.

Measurement precision and reliability in craniofacial anthropometry: implications and suggestions for clinical applications.

Abstract: Craniofacial anthropometry has become an important tool used by both clinical geneticists and reconstructive surgeons. Yet little attention has been paid to the potentially serious problem of measurement error. This paper examines intra-observer measurement error and precision (also called repeatability or reliability) for 52 commonly used anthropometric variables of the head and face. Two factors proved critical to reliability: magnitude of the measurement in question and the degree to which its constituant landmarks could be readily identified. Thus, all of the measurement variables with means above 10 cm proved to have good or excellent reliability. In contrast measurement variables with means below 10 cm were more likely to have poor reliability. This trend was especially evident in variables with means of 6 cm or less where 18 of the 20 variables in this range had poor reliability. The least reliable variables were those like philtrum breadth, columella breadth, and nasal root breadth that combine small magnitude with difficult to define landmarks. While these results suggest that it may be prudent to avoid using craniofacial variables with small dimensions this may be neither practical nor desirable. In such cases repeat measurements may be the best means for optimizing reliability.

Applied reliability assessment in electric power systems

Abstract: This book contains a collection of reprints concerning applied reliability assessment in electric power systems. It includes information about: general capacity assessment; composite system reliability evaluation; transmission and distribution system reliability; and reliability cost/worth.

Design and Analysis of Reliability Studies—the Statistical Evaluation of Measurement Errors

Abstract: Longitudinal Study, a study of the role of birthweight in areal variations in infant mortality, and increased attention to the mortality of migrants, and variations according to place of birth. The examination ofmortality from selected causes back to 1921 shows how long some of the variations between areas have persisted. It is perhaps a pity that the authors have not paid more attention to the influence of age in variation between areas. The use of the SMR as a summary measure implies that the ratio of death rates in two populations is constant over age strata, or at least not sufficiently variable as to make the SMR misleading. It is interesting that the regional variation in \"all cause\" mortality is rather wider for the age groups 15-64 than for 65 and over, but this finding is only briefly commented on. Local authority areas were used as the main units of analysis, although it was recognised that they are internally heterogeneous with regard to their social, economic, and environmental characteristics. Such heterogeneity inevitably limits investigators' ability to explain the variations in mortality that are observed. The suggestion that future volumes may make more use of smaller areas such as wards is therefore welcome. Such minor criticisms do not detract seriously from the value ofthis volume, which will be of interest to epidemiologists, public health specialists, and anyone interested in geographical variations in health.

RELRAD-an analytical approach for distribution system reliability assessment

Abstract: The use of reliability analysis within the framework of distribution system planning is addressed. A specific model for reliability calculations in radially operated distribution systems is presented. Due to increased outage costs in terms of specific costs of nondelivered power and energy (NDP and NDE), an increased part of system operating costs is related to reliability aspects. Customer's outage costs, based on the willingness-to-pay principle, are given the same principal treatment as power system electrical losses. This approach is becoming generally accepted by the power companies in Norway. The reliability model is based on an analytical approach, connecting component failures to load point outages. The description is based on statistical distributions. >

Reliability and feasibility of measuring medical interviewing skills: the revised Maastricht History-Taking and Advice Checklist.

Abstract: Medical interviewing skills are integral to good medical care. In order to measure these skills an instrument has been developed, called the Maastricht History-Taking and Advice Checklist (MAAS). It has been studied with regard to interrater reliability and validity. In this study a revised version of the MAAS (MAAS-R), a check-list of concrete interview behaviour, has been investigated concerning feasibility and reliability for examination purposes. Audio-recordings were obtained of 24 doctors, each interviewing eight different standardized patients. The recordings were independently scored by three general practitioners trained in using the MAAS-R. The results of generalizability analysis, considering the influences of doctors, cases and raters, are encouraging. In order to overcome case-specificity feasible and reliable measurement can be accomplished with 8-10 cases in 2-21/2 hours of testing time, each case being scored by a different rater. Reliability improves considerably if assessment is restricted to basic interviewing skills.

Robot reliability and safety

Abstract: Contents: Introduction.- Introduction to Reliability and Safety.- Introduction to Robotics.- Robot Accidents.- Fundamentals of Robot Safety.- Topics in Robot Safety.- Human Factors in Robotics.- Robot Reliability.- Robot Maintenance.- Failure Data and Analysis.- Robot Economics.- Robot Testing and Information Related to Robots.- Appendix.