Showing papers on "Reliability (statistics) published in 2007"

Answering the Call for a Standard Reliability Measure for Coding Data

Abstract: In content analysis and similar methods, data are typically generated by trained human observers who record or transcribe textual, pictorial, or audible matter in terms suitable for analysis. Conclusions from such data can be trusted only after demonstrating their reliability. Unfortunately, the content analysis literature is full of proposals for so-called reliability coefficients, leaving investigators easily confused, not knowing which to choose. After describing the criteria for a good measure of reliability, we propose Krippendorff's alpha as the standard reliability measure. It is general in that it can be used regardless of the number of observers, levels of measurement, sample sizes, and presence or absence of missing data. To facilitate the adoption of this recommendation, we describe a freely available macro written for SPSS and SAS to calculate Krippendorff's alpha and illustrate its use with a simple example.

Fundamentals of Social Research Methods: An African Perspective

Abstract: The different methods of acquiring knowledge the scientific method applied to social reality problem conception and background information variables and hypothesis formulation the types of research community-centred research research design sampling data collection - basic concepts and techniques research ethics reliability and validity of measurements interpretation of results and writing a research report concluding remarks.

Essential elements of questionnaire design and development.

Abstract: Aims The aims of this paper were (1) to raise awareness of the issues in questionnaire development and subsequent psychometric evaluation, and (2) to provide strategies to enable nurse researchers to design and develop their own measure and evaluate the quality of existing nursing measures. Background The number of questionnaires developed by nurses has increased in recent years. While the rigour applied to the questionnaire development process may be improving, we know that nurses are still not generally adept at the psychometric evaluation of new measures. This paper explores the process by which a reliable and valid questionnaire can be developed. Methods We critically evaluate the theoretical and methodological issues associated with questionnaire design and development and present a series of heuristic decision-making strategies at each stage of such development. The range of available scales is presented and we discuss strategies to enable item generation and development. The importance of stating a priori the number of factors expected in a prototypic measure is emphasized. Issues of reliability and validity are explored using item analysis and exploratory factor analysis and illustrated using examples from recent nursing research literature. Conclusion Questionnaire design and development must be supported by a logical, systematic and structured approach. To aid this process we present a framework that supports this and suggest strategies to demonstrate the reliability and validity of the new and developing measure. Relevance to clinical practice In developing the evidence base of nursing practice using this method of data collection, it is vital that questionnaire design incorporates preplanned methods to establish reliability and validity. Failure to develop a questionnaire sufficiently may lead to difficulty interpreting results, and this may impact upon clinical or educational practice. This paper presents a critical evaluation of the questionnaire design and development process and demonstrates good practice at each stage of this process.

Reliability analysis for wind turbines

Abstract: Modern wind turbines are complex aerodynamic, mechanical and electrical machines incorporating sophisticated control systems. Wind turbines have been erected in increasing numbers in Europe, the USA and elsewhere. In Europe, Germany and Denmark have played a particularly prominent part in developing the technology, and both countries have installed large numbers of turbines. This article is concerned with understanding the historic reliability of modern wind turbines. The prime objective of the work is to extract information from existing data so that the reliability of large wind turbines can be predicted, particularly when installed offshore in the future. The article uses data collected from the Windstats survey to analyse the reliability of wind turbine components from historic German and Danish data. Windstats data have characteristics common to practical reliability surveys; for example, the number of failures is collected for each interval but the number of turbines varies in each interval. In this article, the authors use reliability analysis methods which are not only applicable to wind turbines but relate to any repairable system. Particular care is taken to compare results from the two populations to consider the validity of the data. The main purpose of the article is to discuss the practical methods of predicting large-wind-turbine reliability using grouped survey data from Windstats and to show how turbine design, turbine configuration, time, weather and possibly maintenance can affect the extracted results. Copyright © 2006 John Wiley &Sons, Ltd.

Validity and Reliability of Korean Version of International Physical Activity Questionnaire (IPAQ) Short Form.

Abstract: Validity and Reliability of Korean Version of International Physical Activity Questionnaire (IPAQ) Short FormJi Yeon Oh, D.D.S., Ph.D., Yun Jun Yang, M.D., PH.D.*†, Byung Sung Kim, M.D., PH.D.**, Jae Hun Kang, M.D., PH.D.*

A new brief instrument for assessing decisional capacity for clinical research.

Abstract: Context There is a critical need for practical measures for screening and documenting decisional capacity in people participating in different types of clinical research. However, there are few reliable and validated brief tools that could be used routinely to evaluate individuals' capacity to consent to a research protocol. Objective To describe the development, testing, and proposed use of a new practical instrument to assess decision-making capacity: the University of California, San Diego Brief Assessment of Capacity to Consent (UBACC). The UBACC is intended to help investigators identify research participants who warrant more thorough decisional capacity assessment and/or remediation efforts prior to enrollment. Design, Setting, and Participants We developed the UBACC as a 10-item scale that included questions focusing on understanding and appreciation of the information concerning a research protocol. It was developed and tested among middle-aged and older outpatients with schizophrenia and healthy comparison subjects participating in research on informed consent. In an investigation of reliability and validity, we studied 127 outpatients with schizophrenia or schizoaffective disorder and 30 healthy comparison subjects who received information about a simulated clinical drug trial. Internal consistency, interrater reliability, and concurrent (criterion) validity (including correlations with an established instrument as well as sensitivity and specificity relative to 2 potential “gold standard” criteria) were measured. Main Outcome Measures Reliability and validity of the UBACC. Results The UBACC was found to have good internal consistency, interrater reliability, concurrent validity, high sensitivity, and acceptable specificity. It typically took less than 5 minutes to administer, was easy to use and reliably score, and could be used to identify subjects with questionable capacity to consent to the specific research project. Conclusion The UBACC is a potentially useful instrument for screening large numbers of subjects to identify those needing more comprehensive decisional capacity assessment and/or remediation efforts.

On the reliability and validity of manual muscle testing: a literature review

Abstract: Introduction A body of basic science and clinical research has been generated on the manual muscle test (MMT) since its first peer-reviewed publication in 1915. The aim of this report is to provide an historical overview, literature review, description, synthesis and critique of the reliability and validity of MMT in the evaluation of the musculoskeletal and nervous systems.

Recent Advances in Optimal Reliability Allocation

Abstract: Reliability has become a greater concern in recent years, because high-tech industrial processes with ever increasing levels of sophistication comprise most engineering systems today. To keep pace with this rapidly developing field, this paper provides a broad overview of recent research on reliability optimization problems and their solution methodologies. In particular, we address issues related to: 1) universal generating-function-based optimal multistate system design; 2) percentile life employed as a system performance measure; 3) multiobjective optimization of reliability systems, especially with uncertain component-reliability estimations; and 4) innovation and improvement in traditional reliability optimization problems, such as fault-tolerance mechanism and cold-standby redundancy-involved system design. New developments in optimization techniques are also emphasized in this paper, especially the methods of ant colony optimization and hybrid optimization. We believe that the interesting problems that are reviewed here are deserving of more attention in the literature. To that end, this paper concludes with a discussion of future challenges related to reliability optimization

The benefits of imperfect diagnostic automation: a synthesis of the literature

Abstract: This review of the literature examines, in a quantitative fashion, how the level of imperfection or unreliability of diagnostic automation affects the performance of the human operator who is jointly consulting that automation and the raw data itself. The data from 20 different studies were used to generate 35 different data points that compared performance with varying levels of unreliability, with that of a non-automated baseline condition. A regression analysis of benefits/costs relative to baseline was carried out, and revealed a strong linear function of benefits with reliability. The analysis revealed that a reliability of 0.70 was the ‘crossover point’ below which unreliable automation was worse than no automation at all. The analysis also revealed that performance was more strongly affected by reliability in high workload conditions, implicating the role of workload-imposed automation dependence in producing this relationship, and suggesting that humans tend to protect performance of concurrent ta...

A Psychometric Study of the Index of Learning Styles

Abstract: A study was conducted on the Felder-Soloman Index of Learning Styles© (ILS) to assess reliability, factor structure, and construct validity as well to determine whether changing its dichotomous response scale to a five-option response scale would improve reliability and validity. Data collected in this study had internal consistency reliability ranging from 0.55 to 0.77 across the four learning style scales of the ILS. Factor analysis revealed that multiple factors were present within three of the learning style scales, which correspond to known aspects of the scale definitions. The factor analysis and direct feedback from students on whether they felt their scores accurately represented their learning preferences provide evidence of construct validity for the ILS. Changing the response scale improved reliability, but it did not change the factor structure substantially nor did it affect the strength of the evidence for construct validity based on student feedback.

Stochastic Ageing and Dependence for Reliability

Abstract: (2007). Stochastic Ageing and Dependence for Reliability. Technometrics: Vol. 49, No. 2, pp. 222-222.

Encyclopedia of statistics in quality and reliability

Abstract: Encyclopedia statistics in quality and reliability , Encyclopedia statistics in quality and reliability , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Improving Wind Turbine Gearbox Reliability

Abstract: NOTICE The submitted manuscript has been offered by an employee of the Midwest Research Institute (MRI), a contractor of the US Government under Contract No. DE-AC36-99GO10337. Accordingly, the US Government and MRI retain a nonexclusive royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US Government purposes. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Summary This paper describes a new research and development initiative to improve gearbox reliability in wind turbines begun at the National Renewable Energy Laboratory (NREL) in Golden, Colorado, USA. The approach involves a collaboration of NREL staff, expert consultants, and partners from the wind energy industry who have an interest in improving gearbox reliability. The membership of this collaborative is still growing as the project becomes more defined, but the goal is to include representatives ranging from the operators, owners, wind turbine manufacturers, gearbox manufacturers, bearing manufacturers, consultants, and lubrication industries. The project is envisioned to be a multi-year comprehensive testing and analysis effort. This will include complementary laboratory and field testing on a 600 to 750-kW turbine and gearbox of a configuration that exhibits reliability problems common to a broad population of turbines. The project will target deficiencies in the design process that are contributing to substantial shortfalls in service life for most designs. New design-analysis tools will be developed to model the test configuration in detail. This will include using multi-body dynamic analysis to model wind turbine loading, coupled to internal loading and deformations of the gearbox. Intellectual property conflicts will be minimized by maintaining a test configuration that does not replicate any specific manufacturer's wind turbine model precisely, but represents a common configuration.

Increasing the Reliability of Reliability Diagrams

Abstract: The reliability diagram is a common diagnostic graph used to summarize and evaluate probabilistic forecasts. Its strengths lie in the ease with which it is produced and the transparency of its definition. While visually appealing, major long-noted shortcomings lie in the difficulty of interpreting the graph visually; for the most part, ambiguities arise from variations in the distributions of forecast probabilities and from various binning procedures. A resampling method for assigning consistency bars to the observed frequencies is introduced that allows for immediate visual evaluation as to just how likely the observed relative frequencies are under the assumption that the predicted probabilities are reliable. Further, an alternative presentation of the same information on probability paper eases quantitative evaluation and comparison. Both presentations can easily be employed for any method of binning.

Reliability-Based Transmission Reinforcement Planning Associated With Large-Scale Wind Farms

Abstract: The reliability impacts of a highly variable energy source such as wind power is an important aspect that needs to be assessed as wind power penetration becomes increasingly significant. Bulk electric system (BES) reliability analysis associated with wind energy conversion systems (WECS) provides an opportunity to investigate the reliability benefits at potential BES connection points in close proximity to the wind power development area. A bulk electric system can encounter transmission capacity limitation problems when a large-scale WECS is connected to a weak transmission area. In this case, transmission reinforcement may be required in order to increase the system capability to absorb more wind power at specified locations. BES reliability analysis associated with large-scale wind farms as demonstrated in this paper can assist system planners to create potential transmission reinforcement schemes to facilitate large-scale WECS additions to a bulk system. Reliability cost/worth analysis is also incorporated in the examination of reinforcement alternatives. A sequential Monte Carlo simulation approach is used as this methodology can facilitate a time series modeling of wind speeds and also provides accurate frequency and duration assessments. An auto-regressive moving average (ARMA) time series model is used to simulate hourly wind speeds

Margins of Error

Abstract: Preface. Acknowledgements. Foreward. 1. Measurement Errors in Surveys. 2. Sources of Survey Measurement Error. 3. Reliability Theory for Survey Measures. 4. Reliability Methods for Multiple Measures. 5. Longitudinal Methods for Reliability Estimation. 6. Using Longitudinal Data to Estimate Reliability Parameters. 7. The Source and Content of Survey Questions. 8. Survey Question Context. 9. Formal Properties of Survey Questions. 10. Attributes of Respondents. 11. Reliability Estimation for Categorical Latent Variables. 12. Final Thoughts and Future Directions. Appendix. References. Index.

Managing the unexpected: resilient performance in an age of uncertainty, second edition

Abstract: Managing the UnexpectedAuthors Karl Weick and Kathleen Sutcliffe answer this question by pointing to high reliability organizations (HROs), such as emergency rooms in hospitals, flight operations of aircraft carriers, and firefighting units, as models to follow. These organizations have developed ways of acting and styles of learning that enable them to manage the unexpected better than other organizations. Thoroughly revised and updated, the second edition of the groundbreaking book Managing the Unexpected uses HROs as a template for any institution that wants to better organize for high reliability.

An Introduction to the Basics of Reliability and Risk Analysis

Abstract: Basic Concepts of Safety and Risk Analysis Methods for Hazard Identification Basics of Probability Theory for Applications to Reliability and Risk Analysis Reliability of Simple Systems Availability and Maintainability Fault Tree Analysis Event Tree Analysis Estimation of Reliability Parameters from Experimental Data.

Reliability of four scales on balance disorders in persons with multiple sclerosis

Abstract: Purpose. Balance rehabilitation is an important component of the retraining program in people with multiple sclerosis (MS). Measuring balance is fundamental for an accurate assessment and therapy selection. The aim of this study was to compare interrater and test-retest reliability of the Berg Balance Scale, the Dynamic Gait Index, the Dizziness Handicap Inventory and the Activities-specific Balance Confidence.Method. A group of 25 persons were enrolled in the study. The group consisted of 8 males and 17 females, mean age 41.7 years (12.5 years, SD). The onset of pathology was 8.7 years (8.8 years SD) before the beginning of the study. To assess the test-retest reliability two consecutive assessments were collected by the same rater. To assess the inter-rater reliability persons were concurrently assessed by two raters.Results. The Intraclass Correlation Coefficients (ICCs) for interrater reliability ranged between 0.94 and 0.96. The ICCs for test-retest reliability ranged between 0.85 and 0.96.Conclusion...

Reliability of Wind Turbines

Abstract: With the rapid expansion of wind energy use in Germany over the past fifteen years, extensive developments in wind turbine technology have taken place. The new technology has achieved such a level of quality, that wind turbines obtain a technical availability of 98 percent. This means that an average wind turbine (WT) will be inactive for around one week per year for repairs and maintenance. Considering that the WTs operate over years without operating personnel, this average downtime seems short. The paper gives some figures about reliability of wind turbines, failures and downtimes for wind turbines and components.

On the search for reliable performance indicators in game sports

Abstract: This article addresses the reliability of performance indicators in game sports. In this context, reliability is invariably treated from a technical point of view as a question of observer agreemen...