Showing papers on "Reliability (statistics) published in 1986"
Journal Article•
TL;DR: This book gives the detailed procedures officially recommended by ISI for the various analysis of milk and milk products, as demonstrated by the ISI by thorough testing.
Abstract: This book gives the detailed procedures officially recommended by ISI for the various analysis of milk and milk products. Nutritionists, Biochemists, chemists, and quality control personnels depend upon the official methods of analysists, the ISI reliability of methodology is the main concern: This has been demonstrated by the ISI by thorough testing.
2,495 citations
TL;DR: In this paper, a comprehensive framework for the analysis of structural reliability under incomplete probability information is presented, consistent with the philosophy of Ditlevsen's generalized reliability index and complements existing second-moment and full-distribution structural reliability theories.
Abstract: A comprehensive framework is set forth for the analysis of structural reliability under incomplete probability information. Under stipulated requirements of consistency, invariance, operability, and simplicity, a method is developed to incorporate in the reliability analysis incomplete probability information on random variables, including moments, bounds, marginal distributions, and partial joint distributions. The method is consistent with the philosophy of Ditlevsen’s generalized reliability index and complements existing second-moment and full-distribution structural reliability theories.
810 citations
TL;DR: The reliability and validity of the Functional Status Questionnaire (FSQ), a brief, standardized, self-administered questionnaire designed to provide a comprehensive and feasible assessment of physical, psychological, social and role function in ambulatory patients, are examined.
Abstract: A comprehensive functional assessment requires thorough and careful inquiry, which is difficult to accomplish in most busy clinical practices. This paper examines the reliability and validity of the Functional Status Questionnaire (FSQ), a brief, standardized, self-administered questionnaire designed to provide a comprehensive and feasible assessment of physical, psychological, social and role function in ambulatory patients. The FSQ can be completed and computer-scored in minutes to produce a one-page report which includes six summated-rating scale scores and six single-item scores. The clinician can use this report both to screen for and to monitor patients’ functional status. In this study, the FSQ was administered to 497 regular users of Boston’s Beth Israel Hospital’ Healthcare Associates and 656 regular users of 76 internal medicine practices in Los Angeles. The data demonstrate that the FSQ produces reliable sub-scales with construct validity. The authors believe the FSQ addresses many of the problems behind the slow diffusion into primary care of systematic functional assessment.
553 citations
Book•
01 May 1986
TL;DR: Reliability Analysis of Structural Systems by the ?-Unzipping Method and Various Problems of Probability-Based Optimum Design.- 8.1.
Abstract: 1. Fundamentals of Structural Reliability Theory.- 1.1 Introduction.- 1.2 Modelling of Load and Resistance Variables.- 1.3 The Fundamental Case.- 1.4 Basic Variables and Failure Surfaces.- 1.5 The Hasofer and Lind Reliability Index.- 1.6 Estimate of the Reliability of Single Elements.- 1.7 Non-Normal Basic Variables.- 2. Modelling of Structural Systems.- 2.1 Introduction.- 2.2 Modelling of Structural Elements.- 2.3 Fundamental Systems.- 2.4 Systems Modelling At Level N.- 2.5 Systems Modelling at Mechanism Level.- 2.6 Formal Representation of Systems.- 2.7 Approximations of the Multivariate Normal Distribution Function.- 3. Reliability of Series Systems.- 3.1 Introduction.- 3.2 Probability of Failure of Series Systems.- 3.3 Reliability Bounds for Series Systems.- 3.4 Series Systems with Equally Corelated Elements.- 3.5 Series Systems with Unequally Correlated Elements.- 3.6 The Hohenbichler Approximation.- 4. Reliability of Parallel Systems.- 4.1 Introduction.- 4.2 Probability of Failure of Parallel Systems.- 4.3 Reliability Bounds for Parallel Systems.- 4.4 Equivalent Linear Safety Margins for Parallel Systems.- 4.5 Parallel Systems with Equally Correlated Elements.- 4.6 Parallel Systems with Unequally Correlated Elements.- 5. Automatic Generation of Safety Margins.- 5.1 Introduction.- 5.2 Generation of Safety Margins for Truss Structures.- 5.3 Generation of Safety Margins for Frame Structures Subjected to Single Load Effect.- 5.4 Generation of Safety Margins for Frame Structures Subjected to Combined Load Effects.- 5.5 Generation of Fundamental Mechanisms for Elastoplastic Structures.- 6. Reliability Analysis of Structural Systems by the ?-Unzipping Method.- 6.1 Introduction.- 6.2 Non-Normal Basic Variables.- 6.3 Reliability of Single Elements.- 6.4 Estimate of Systems Reliability at Level 1.- 6.5 Estimate of Systems Reliability at Level 2.- 6.6 Estimate of Systems Reliability at Level N > 2.- 6.7 Estimate of Systems Reliability at Mechanism Level.- 7. The Branch-and-Bound Method.- 7.1 Introduction.- 7.2 Failure Paths and Failure Modes.- 7.3 The Concept of the Branch-and-Bound Method.- 7.4 Identification of Dominant Failure Paths.- 7.5 Evaluation of the Systems Reliability.- 7.6 Application to Offshore Structures.- 7.7 Further Developments and Numerical Examples.- 8. Optimization of Structural Systems.- 8.1 Introduction.- 8.2 Probability-Based Optimum Design Problem.- 8.3 Various Problems of Probability-Based Optimum Design.- 8.4 Optimum Design Based on Element Reliability.- 8.5 Optimal Design by The ?-Unzipping Method.- Appendix the Standard Normal Distribution Function c.
416 citations
TL;DR: Some techniques are presented which form the basis of a partial solution to the problem of knowing which, if any, of the competing predictions are trustworthy in a reliability growth context.
Abstract: Different software reliability models can produce very different answers when called on to predict future reliability in a reliability growth context. Users need to know which, if any, of the competing predictions are trustworthy. Some techniques are presented which form the basis of a partial solution to this problem. Rather than attempting to decide which model is generally best, the approach adopted allows a user to decide on the most appropriate model for each application.
296 citations
TL;DR: An Industry Assessment Study (IAS) was conducted to evaluate the present reliability of powerhouse motors and to identify design and operational characteristics which, through advanced development, offer the potential of increased motor, and therefore, power plant reliability.
Abstract: An Industry Assessment Study (IAS) was conducted to evaluate the present reliability of powerhouse motors and to identify design and operational characteristics which, through advanced development, offer the potential of increased motor, and therefore, power plant reliability. The primary objective of the IAS was to collect, analyze, and interpret candid, detailed information concerning motor application, operating factors, installation, manufacturer, failures and causes of failures. The survey data covers 6312 motors from 168 generating units representing 65 utilities. This data covers 40 percent of the population surveyed. The large quantity of data allows a meaningful analysis when it is broken down into smaller groupings.
287 citations
TL;DR: The proposed models will enable us to evaluate software reliability more realistically and consider the relationship between the software reliability growth and the effect of testing-effort.
Abstract: Many software reliability growth models have been proposed in the past decade. Those models tacitly assume that testing-effort expenditures are constant throughout software testing. This paper develops realistic software reliability growth models incorporating the effect of testing-effort. The software error detection phenomenon in software testing is modeled by a nonhomogeneous Poisson process. The software reliability assessment measures and the estimation methods of parameters are investigated. Testing-effort expenditures are described by exponential and Rayleigh curves. Least-squares estimators and maximum likelihood estimators are used for the reliability growth parameters. The software reliability data analyses use actual data. The software reliability growth models with testing-effort can consider the relationship between the software reliability growth and the effect of testing-effort. Thus, the proposed models will enable us to evaluate software reliability more realistically.
263 citations
TL;DR: The Computer Attitude Scale (CAS) as mentioned in this paper was created to measure positive and negative attitudes toward computers, and the reliability and validity of the CAS were evaluated by multiple groups of subjects.
259 citations
TL;DR: The modified Roland Scale appeared to have reliability, validity, and sensitivity that were at least as good as the overall SIP or its major subscales, although the Roland Scale did not measure psychosocial function well.
Abstract: Several scales exist for measuring functional status in patients with low-back pain (LBP). There are few comparative data, however, to suggest which scales may perform best. We compared the Sickness Impact Profile (SIP), its major subscales, and a short index derived from the SIP (a slight modification of an index proposed by Roland) with regard to reliability, validity, and sensitivity to change. Walk-in patients with mechanical LBP (n = 136) completed the entire SIP at an index visit and again 3 weeks later. The examination of individual items allowed scoring for the derivative scales. The modified Roland Scale appeared to have reliability, validity, and sensitivity that were at least as good as the overall SIP or its major subscales. Although the Roland Scale did not measure psychosocial function well, this aspect of functioning changed less over time than physical function.
245 citations
TL;DR: In this paper, the authors propose and empirically test a model of the relationships among research design variables and the psychometric criteria of reliability, convergent validity, and discriminative similarity.
Abstract: The purpose of the article is to propose and empirically test a model of the relationships among research design variables and the psychometric criteria of reliability, convergent validity, discrim...
TL;DR: The Eating Self-Efficacy Scale (ESES) as mentioned in this paper is a self-efficacy scale based on the Bandura (1977a) selfefficacy theory and has been used for eating disorders.
Abstract: Following from Bandura's (1977a) self-efficacy theory, an Eating Self-Efficacy Scale (ESES) was developed and its psychometric properties established. Factor analysis of the 25-item scale yielded two reliable factors—one concerned with eating when experiencing negative affect (NA) and the other with eating during socially acceptable circumstances (SAC). The ESES demonstrated good internal consistency, test-retest reliability, and convergent validity. A clinical study using this measure found that increases in ESES scores were significantly related to weight losses among weight loss program participants. A laboratory study using a mood induction procedure found that NA subscale scores predicted food consumption irrespective of whether negative affect was induced. This finding may indicate that people have difficulty accurately discriminating the specific circumstances under which their eating difficulties occur and/or that eating difficulties tend to be global in nature. The significant correlation of the two ESES subscales (r =.39, p <.001) supports these possibilities. The clinical and research utility of the ESES and the implications of the findings are discussed.
TL;DR: Results support the reliability of the CMI for use in epidemiological and clinical studies and users are cautioned about the subjectivity of numerous items within the C MI.
Abstract: The Craniomandibular Index (CMI) was developed to provide a standardized measure of severity of problems in mandibular movement, TMJ noise, and muscle and joint tenderness for use in epidemiological and clinical outcome studies. The instrument was designed to have clearly defined objective criteria, simple clinical methods, and ease in scoring; it is divided into the Dysfunction Index and the Palpation Index. Inter-rater reliability (three raters) and intra-rater reliability (19 patients examined twice by one rater) were tested to determine whether the instrument has operational definitions sufficiently precise to allow for consistency in use between different raters and with one rater over time. Intraclass Correlation Coefficient for inter-rater reliability was 0.84 for the Dysfunction Index, 0.87 for the Palpation Index, and 0.95 for the CMI. Correlation for intra-rater reliability was 0.92 for the Dysfunction Index, 0.86 for the Palpation Index, and 0.96 for the CMI. These results support the reliability of the CMI for use in epidemiological and clinical studies. Users are cautioned about the subjectivity of numerous items within the CMI and the strict methodological guidelines that must be followed in order to assure accuracy and reproducibility of results.
IBM1
TL;DR: A description is given of a procedure for certifying the reliability of software before its release to users, which includes a life cycle of executable product increments, representative statistical testing, and a standard estimate of the MTTF of the product at the time of its release.
Abstract: A description is given of a procedure for certifying the reliability of software before its release to users. The ingredients of this procedure are a life cycle of executable product increments, representative statistical testing, and a standard estimate of the MTTF (mean time to failure) of the product at the time of its release. The authors also discuss the development of certified software products and the derivation of a statistical model used for reliability projection. Available software test data are used to demonstrate the application of the model in certification process.
TL;DR: The test-retest reliability of the Minnesota Leisure Time Physical Activity Questionnaire corroborates its utility in epidemiologic research and indicates a slight, nonsignificant drop in reported leisure time energy expenditure between the test and the retest.
Book•
01 Jan 1986TL;DR: In this article, the exponential failure model Gamma and Weibull Distributions Normal and Related Distributions Mixture Distributions and Competing Risks Tests of Hypotheses and Confidence Intervals Bayes Estimators Bayesian Approximation and Reliability Estimation Bayesian Intervals for Parameters and reliability Functions Reliability of Series/Parallel Systems Appendixes References Author Index Subject Index.
Abstract: Foreword Preface Introduction Exponential Failure Model Gamma and Weibull Distributions Normal and Related Distributions Mixture Distributions and Competing Risks Tests of Hypotheses and Confidence Intervals Bayes Estimators Bayesian Approximation and Reliability Estimation Bayesian Intervals for Parameters and Reliability Functions Reliability of Series/Parallel Systems Appendixes References Author Index Subject Index.
TL;DR: The RTS is extended by including more factors and system conditions which may be included in the reliability evaluation of generating systems to create a wider set of consistent data.
Abstract: This paper outlines some of the restrictions which currently exist in the generation data of the IEEE Reliability Test System (RTS) The paper extends the RTS by including more factors and system conditions which may be included in the reliability evaluation of generating systems These extensions create a wider set of consistent data The paper also includes generation reliability indices for the base and extended RTS These indices have been evaluated without any approximations in the evaluation process and therefore provide a set of exact indices against which the results from alternative and approximate methods can be compared
01 Jun 1986
TL;DR: It is demonstrated that predictions and confidence ratings have often been confused in the literature.
Abstract: Experts are often asked to assess two different kinds of probabilities. One is THE PROBABILITY THAT SOMETHING WILL HAPPEN: rain, hitting an oil well, dying in an operation, tube fracture, a total melt-down. We will call these probabilities “predictions”. Experts’ predictions are widely used in all sorts of personal and public decision making. Two examples of formal usage of expert opinion are risk analyses and expert systems used for diagnostic tasks. The second kind of probability assessed by experts is THE PROBABILITY THAT THEIR ANSWERS ARE CORRECT. We will call these probabilities “confidence ratings”. A little later we will demonstrate that predictions and confidence ratings have often been confused in the literature.
TL;DR: In this paper, an extension of the reliability diagram is described, in which the accuracy, resolution, and skill, as well as the reliability, of probability forecasts can be depicted, and these geometrical representations are directly related to quantitative measures of the respective attributes.
TL;DR: In this paper, a Markov process is used to solve a sequence of uni-phase systems with appropriate initial conditions, and a method of solution is presented and illustrated by examples.
Abstract: A quantitative reliability model for a phased mission system is developed using a Markov process. Two cases for the mission-phase change times are assumed: 1) to be known in advance and 2) to be random variables. A method of solution is presented and illustrated by examples. The solution of phased-mission systems is equivalent to solving a sequence of uni-phase systems with appropriate initial conditions.
Patent•
13 Aug 1986
TL;DR: In this paper, a Reliability and Maintainability Indicator (RAMI) is proposed to predict the remaining time of operation before failure by having key parameters of an equipment monitored by applicable transducers to sense measurands periodically over a period of time.
Abstract: A Reliability and Maintainability Indicator (RAMI) is disclosed which effectively predicts the remaining time of operation of a system, equipment, component, or device before it would fail to perform its intended functions. The ability of RAMI to predict the remaining time of operation before failure is accomplished by having key parameters of an equipment monitored by applicable transducers to sense measurands periodically over a period of time. Then, these measurands are analyzed to project when they would reach pre-established limits which would indicate equipment failure or serious degradation resulting in the equipment failing to perform its intended functions. A micro-processor based computer is used to analyze the measurands, as required, and correlates them, by means of mathematical extropolation to obtain the time at which failure, or a pre-established limit of degradation of the equipment is expected to occur. Visual and audio means are provided to indicate that the monitored equipment is operating properly or that a pre-determined degree of degradation has occured or is expected to occur by a given time.
TL;DR: Using the definitions for the patient's expectations, feelings and fears, a method was devised for scoring video-taped interviews for the degree of 'patient-centredness' and proved to have good inter-observer reliability.
Abstract: In this article, the patient-centred clinical method is described in operational terms. Definitions are given for the patient's expectations, feelings and fears. The physician behaviours described are: facilitations, acknowledgements, cut-offs and returns. Using the definitions, a method was devised for scoring video-taped interviews for the degree of 'patient-centredness'. The method proved to have good inter-observer reliability.
TL;DR: In this paper, the authors present the last five to ten years of development within the field of structural reliability theory with particular attention to structural systems, including single element reliability, series systems reliability, parallel systems and general systems reliability.
TL;DR: “Skewness” is a test for very early local defects, and “spatial correlation” provides a measurement of the clustering of any local defects that may be present.
Abstract: Statistical methods for the evaluation of quantitative visual fields are presented in addition to a mathematical description of the calculation of different visual field indices. The "mean defect" is important for diffuse damage as well as for follow-up in advanced stages. "Short-term fluctuation" provides information about the reliability of the results as well as about possible early damage. "Corrected loss variance" quantifies local defects in an early stage; it also separates real local defects from increased scatter. "Skewness" is a test for very early local defects, and "spatial correlation" provides a measurement of the clustering of any local defects that may be present.
TL;DR: The conclusion is that the Severity of Illness Index is a reliable and valid tool for measuring inpatient severity of illness.
Abstract: The authors discuss the objectives and definition of the Severity of Illness Index, which has been developed and refined at The Johns Hopkins University over the past 5 years. In addition, the training program for raters, the method used to ascertain reliability, and data from reliability testing in
TL;DR: Questions regarding the application of the kappa statistic in assessing the reliability of measures to classify patients are discussed and suggestions for a more comprehensive approach to the study of the psychometric properties of measures of patient classification are offered.
Abstract: Selected issues regarding the application of the kappa statistic in assessing the reliability of measures to classify patients are discussed. Data are used to illustrate how the methods used to estimate reliability can influence the resulting coefficient. Suggestions for a more comprehensive approac
TL;DR: The high levels of reliability and validity in preliminary testing indicate that the Laffrey Health Conception Scale warrants further development and use with different populations.
Abstract: Described in this paper are the development, reliability, and validity of an instrument, the Laffrey Health Conception Scale to measure individual perceptions of the meaning of health. The instrument measures four dimensions of health conception: clinical, functional/role performance, adaptive, and eudaimonistic. A score is obtained for each dimension as well as a total score for the four dimensions. The high levels of reliability and validity in preliminary testing indicate that the instrument warrants further development and use with different populations.