Small sample estimation of the reliability function for technical products

NASA Astrophysics Data System (ADS)

Lyamets, L. L.; Yakimenko, I. V.; Kanishchev, O. A.; Bliznyuk, O. A.

2017-12-01

It is demonstrated that, in the absence of big statistic samples obtained as a result of testing complex technical products for failure, statistic estimation of the reliability function of initial elements can be made by the moments method. A formal description of the moments method is given and its advantages in the analysis of small censored samples are discussed. A modified algorithm is proposed for the implementation of the moments method with the use of only the moments at which the failures of initial elements occur.

Mission Reliability Estimation for Repairable Robot Teams

NASA Technical Reports Server (NTRS)

Trebi-Ollennu, Ashitey; Dolan, John; Stancliff, Stephen

2010-01-01

A mission reliability estimation method has been designed to translate mission requirements into choices of robot modules in order to configure a multi-robot team to have high reliability at minimal cost. In order to build cost-effective robot teams for long-term missions, one must be able to compare alternative design paradigms in a principled way by comparing the reliability of different robot models and robot team configurations. Core modules have been created including: a probabilistic module with reliability-cost characteristics, a method for combining the characteristics of multiple modules to determine an overall reliability-cost characteristic, and a method for the generation of legitimate module combinations based on mission specifications and the selection of the best of the resulting combinations from a cost-reliability standpoint. The developed methodology can be used to predict the probability of a mission being completed, given information about the components used to build the robots, as well as information about the mission tasks. In the research for this innovation, sample robot missions were examined and compared to the performance of robot teams with different numbers of robots and different numbers of spare components. Data that a mission designer would need was factored in, such as whether it would be better to have a spare robot versus an equivalent number of spare parts, or if mission cost can be reduced while maintaining reliability using spares. This analytical model was applied to an example robot mission, examining the cost-reliability tradeoffs among different team configurations. Particularly scrutinized were teams using either redundancy (spare robots) or repairability (spare components). Using conservative estimates of the cost-reliability relationship, results show that it is possible to significantly reduce the cost of a robotic mission by using cheaper, lower-reliability components and providing spares. This suggests that the

Program for computer aided reliability estimation

NASA Technical Reports Server (NTRS)

Mathur, F. P. (Inventor)

1972-01-01

A computer program for estimating the reliability of self-repair and fault-tolerant systems with respect to selected system and mission parameters is presented. The computer program is capable of operation in an interactive conversational mode as well as in a batch mode and is characterized by maintenance of several general equations representative of basic redundancy schemes in an equation repository. Selected reliability functions applicable to any mathematical model formulated with the general equations, used singly or in combination with each other, are separately stored. One or more system and/or mission parameters may be designated as a variable. Data in the form of values for selected reliability functions is generated in a tabular or graphic format for each formulated model.

Stability of individual loudness functions obtained by magnitude estimation and production

NASA Technical Reports Server (NTRS)

Hellman, R. P.

1981-01-01

A correlational analysis of individual magnitude estimation and production exponents at the same frequency is performed, as is an analysis of individual exponents produced in different sessions by the same procedure across frequency (250, 1000, and 3000 Hz). Taken as a whole, the results show that individual exponent differences do not decrease by counterbalancing magnitude estimation with magnitude production and that individual exponent differences remain stable over time despite changes in stimulus frequency. Further results show that although individual magnitude estimation and production exponents do not necessarily obey the .6 power law, it is possible to predict the slope of an equal-sensation function averaged for a group of listeners from individual magnitude estimation and production data. On the assumption that individual listeners with sensorineural hearing also produce stable and reliable magnitude functions, it is also shown that the slope of the loudness-recruitment function measured by magnitude estimation and production can be predicted for individuals with bilateral losses of long duration. Results obtained in normal and pathological ears thus suggest that individual listeners can produce loudness judgements that reveal, although indirectly, the input-output characteristic of the auditory system.

Lifetime prediction and reliability estimation methodology for Stirling-type pulse tube refrigerators by gaseous contamination accelerated degradation testing

NASA Astrophysics Data System (ADS)

Wan, Fubin; Tan, Yuanyuan; Jiang, Zhenhua; Chen, Xun; Wu, Yinong; Zhao, Peng

2017-12-01

Lifetime and reliability are the two performance parameters of premium importance for modern space Stirling-type pulse tube refrigerators (SPTRs), which are required to operate in excess of 10 years. Demonstration of these parameters provides a significant challenge. This paper proposes a lifetime prediction and reliability estimation method that utilizes accelerated degradation testing (ADT) for SPTRs related to gaseous contamination failure. The method was experimentally validated via three groups of gaseous contamination ADT. First, the performance degradation model based on mechanism of contamination failure and material outgassing characteristics of SPTRs was established. Next, a preliminary test was performed to determine whether the mechanism of contamination failure of the SPTRs during ADT is consistent with normal life testing. Subsequently, the experimental program of ADT was designed for SPTRs. Then, three groups of gaseous contamination ADT were performed at elevated ambient temperatures of 40 °C, 50 °C, and 60 °C, respectively and the estimated lifetimes of the SPTRs under normal condition were obtained through acceleration model (Arrhenius model). The results show good fitting of the degradation model with the experimental data. Finally, we obtained the reliability estimation of SPTRs through using the Weibull distribution. The proposed novel methodology enables us to take less than one year time to estimate the reliability of the SPTRs designed for more than 10 years.

Reliability of TMS phosphene threshold estimation: Toward a standardized protocol.

PubMed

Mazzi, Chiara; Savazzi, Silvia; Abrahamyan, Arman; Ruzzoli, Manuela

Phosphenes induced by transcranial magnetic stimulation (TMS) are a subjectively described visual phenomenon employed in basic and clinical research as index of the excitability of retinotopically organized areas in the brain. Phosphene threshold estimation is a preliminary step in many TMS experiments in visual cognition for setting the appropriate level of TMS doses; however, the lack of a direct comparison of the available methods for phosphene threshold estimation leaves unsolved the reliability of those methods in setting TMS doses. The present work aims at fulfilling this gap. We compared the most common methods for phosphene threshold calculation, namely the Method of Constant Stimuli (MOCS), the Modified Binary Search (MOBS) and the Rapid Estimation of Phosphene Threshold (REPT). In two experiments we tested the reliability of PT estimation under each of the three methods, considering the day of administration, participants' expertise in phosphene perception and the sensitivity of each method to the initial values used for the threshold calculation. We found that MOCS and REPT have comparable reliability when estimating phosphene thresholds, while MOBS estimations appear less stable. Based on our results, researchers and clinicians can estimate phosphene threshold according to MOCS or REPT equally reliably, depending on their specific investigation goals. We suggest several important factors for consideration when calculating phosphene thresholds and describe strategies to adopt in experimental procedures. Copyright © 2017 Elsevier Inc. All rights reserved.

A particle swarm model for estimating reliability and scheduling system maintenance

NASA Astrophysics Data System (ADS)

Puzis, Rami; Shirtz, Dov; Elovici, Yuval

2016-05-01

Modifying data and information system components may introduce new errors and deteriorate the reliability of the system. Reliability can be efficiently regained with reliability centred maintenance, which requires reliability estimation for maintenance scheduling. A variant of the particle swarm model is used to estimate reliability of systems implemented according to the model view controller paradigm. Simulations based on data collected from an online system of a large financial institute are used to compare three component-level maintenance policies. Results show that appropriately scheduled component-level maintenance greatly reduces the cost of upholding an acceptable level of reliability by reducing the need in system-wide maintenance.

Reliable Function Approximation and Estimation

DTIC Science & Technology

2016-08-16

AUSTIN , TX 78712 08/16/2016 Final Report DISTRIBUTION A: Distribution approved for public release. Air Force Research Laboratory AF Office Of Scientific...UNIVERSITY OF TEXAS AT AUSTIN 101 EAST 27TH STREET STE 4308 AUSTIN , TX 78712 DISTRIBUTION A: Distribution approved for public release. INSTRUCTIONS...AFRL-AFOSR-VA-TR-2016-0293 Reliable Function Approximation and Estimation Rachel Ward UNIVERSITY OF TEXAS AT AUSTIN 101 EAST 27TH STREET STE 4308

Use of Internal Consistency Coefficients for Estimating Reliability of Experimental Tasks Scores

PubMed Central

Green, Samuel B.; Yang, Yanyun; Alt, Mary; Brinkley, Shara; Gray, Shelley; Hogan, Tiffany; Cowan, Nelson

2017-01-01

Reliabilities of scores for experimental tasks are likely to differ from one study to another to the extent that the task stimuli change, the number of trials varies, the type of individuals taking the task changes, the administration conditions are altered, or the focal task variable differs. Given reliabilities vary as a function of the design of these tasks and the characteristics of the individuals taking them, making inferences about the reliability of scores in an ongoing study based on reliability estimates from prior studies is precarious. Thus, it would be advantageous to estimate reliability based on data from the ongoing study. We argue that internal consistency estimates of reliability are underutilized for experimental task data and in many applications could provide this information using a single administration of a task. We discuss different methods for computing internal consistency estimates with a generalized coefficient alpha and the conditions under which these estimates are accurate. We illustrate use of these coefficients using data for three different tasks. PMID:26546100

Estimate of the Reliability in Geological Forecasts for Tunnels: Toward a Structured Approach

NASA Astrophysics Data System (ADS)

Perello, Paolo

2011-11-01

In tunnelling, a reliable geological model often allows providing an effective design and facing the construction phase without unpleasant surprises. A geological model can be considered reliable when it is a valid support to correctly foresee the rock mass behaviour, therefore preventing unexpected events during the excavation. The higher the model reliability, the lower the probability of unforeseen rock mass behaviour. Unfortunately, owing to different reasons, geological models are affected by uncertainties and a fully reliable knowledge of the rock mass is, in most cases, impossible. Therefore, estimating to which degree a geological model is reliable, becomes a primary requirement in order to save time and money and to adopt the appropriate construction strategy. The definition of the geological model reliability is often achieved by engineering geologists through an unstructured analytical process and variable criteria. This paper focusses on geological models for projects of linear underground structures and represents an effort to analyse and include in a conceptual framework the factors influencing such models. An empirical parametric procedure is then developed with the aim of obtaining an index called "geological model rating (GMR)", which can be used to provide a more standardised definition of a geological model reliability.

A Comparison of Three Multivariate Models for Estimating Test Battery Reliability.

ERIC Educational Resources Information Center

Wood, Terry M.; Safrit, Margaret J.

1987-01-01

A comparison of three multivariate models (canonical reliability model, maximum generalizability model, canonical correlation model) for estimating test battery reliability indicated that the maximum generalizability model showed the least degree of bias, smallest errors in estimation, and the greatest relative efficiency across all experimental…

Reliability and Accuracy of Static Parameters Obtained From Ink and Pressure Platform Footprints.

PubMed

Zuil-Escobar, Juan Carlos; Martínez-Cepa, Carmen Belén; Martín-Urrialde, Jose Antonio; Gómez-Conesa, Antonia

2016-09-01

The purpose of this study was to evaluate the accuracy and the intrarater reliability of arch angle (AA), Staheli Index (SI), and Chippaux-Smirak Index (CSI) obtained from ink and pressure platform footprints. We obtained AA, SI, and CSI measurements from ink pedigraph footprints and pressure platform footprints in 40 healthy participants (aged 25.65 ± 5.187 years). Intrarater reliability was calculated for all parameters obtained using the 2 methods. Standard error of measurement and minimal detectable change were also calculated. A repeated-measure analysis of variance was used to identify differences between ink and pressure platform footprints. Intraclass correlation coefficient and Bland and Altman plots were used to assess similar parameters obtained using different methods. Intrarater reliability was >0.9 for all parameters and was slightly higher for the ink footprints. No statistical difference was reported in repeated-measure analysis of variance for any of the parameters. Intraclass correlation coefficient values from AA, SI, and CSI that were obtained using ink footprints and pressure platform footprints were excellent, ranging from 0.797 to 0.829. However, pressure platform overestimated AA and underestimated SI and CSI. Our study revealed that AA, SI, and CSI were similar regardless of whether the ink or pressure platform method was used. In addition, the parameters indicated high intrarater reliability and were reproducible. Copyright © 2016. Published by Elsevier Inc.

Model uncertainty and multimodel inference in reliability estimation within a longitudinal framework.

PubMed

Alonso, Ariel; Laenen, Annouschka

2013-05-01

Laenen, Alonso, and Molenberghs (2007) and Laenen, Alonso, Molenberghs, and Vangeneugden (2009) proposed a method to assess the reliability of rating scales in a longitudinal context. The methodology is based on hierarchical linear models, and reliability coefficients are derived from the corresponding covariance matrices. However, finding a good parsimonious model to describe complex longitudinal data is a challenging task. Frequently, several models fit the data equally well, raising the problem of model selection uncertainty. When model uncertainty is high one may resort to model averaging, where inferences are based not on one but on an entire set of models. We explored the use of different model building strategies, including model averaging, in reliability estimation. We found that the approach introduced by Laenen et al. (2007, 2009) combined with some of these strategies may yield meaningful results in the presence of high model selection uncertainty and when all models are misspecified, in so far as some of them manage to capture the most salient features of the data. Nonetheless, when all models omit prominent regularities in the data, misleading results may be obtained. The main ideas are further illustrated on a case study in which the reliability of the Hamilton Anxiety Rating Scale is estimated. Importantly, the ambit of model selection uncertainty and model averaging transcends the specific setting studied in the paper and may be of interest in other areas of psychometrics. © 2012 The British Psychological Society.

Estimating the Reliability of a Soyuz Spacecraft Mission

NASA Technical Reports Server (NTRS)

Lutomski, Michael G.; Farnham, Steven J., II; Grant, Warren C.

2010-01-01

Once the US Space Shuttle retires in 2010, the Russian Soyuz Launcher and Soyuz Spacecraft will comprise the only means for crew transportation to and from the International Space Station (ISS). The U.S. Government and NASA have contracted for crew transportation services to the ISS with Russia. The resulting implications for the US space program including issues such as astronaut safety must be carefully considered. Are the astronauts and cosmonauts safer on the Soyuz than the Space Shuttle system? Is the Soyuz launch system more robust than the Space Shuttle? Is it safer to continue to fly the 30 year old Shuttle fleet for crew transportation and cargo resupply than the Soyuz? Should we extend the life of the Shuttle Program? How does the development of the Orion/Ares crew transportation system affect these decisions? The Soyuz launcher has been in operation for over 40 years. There have been only two loss of life incidents and two loss of mission incidents. Given that the most recent incident took place in 1983, how do we determine current reliability of the system? Do failures of unmanned Soyuz rockets impact the reliability of the currently operational man-rated launcher? Does the Soyuz exhibit characteristics that demonstrate reliability growth and how would that be reflected in future estimates of success? NASA s next manned rocket and spacecraft development project is currently underway. Though the projects ultimate goal is to return to the Moon and then to Mars, the launch vehicle and spacecraft s first mission will be for crew transportation to and from the ISS. The reliability targets are currently several times higher than the Shuttle and possibly even the Soyuz. Can these targets be compared to the reliability of the Soyuz to determine whether they are realistic and achievable? To help answer these questions this paper will explore how to estimate the reliability of the Soyuz Launcher/Spacecraft system, compare it to the Space Shuttle, and its

IRT-Estimated Reliability for Tests Containing Mixed Item Formats

ERIC Educational Resources Information Center

Shu, Lianghua; Schwarz, Richard D.

2014-01-01

As a global measure of precision, item response theory (IRT) estimated reliability is derived for four coefficients (Cronbach's a, Feldt-Raju, stratified a, and marginal reliability). Models with different underlying assumptions concerning test-part similarity are discussed. A detailed computational example is presented for the targeted…

Influences on and Limitations of Classical Test Theory Reliability Estimates.

ERIC Educational Resources Information Center

Arnold, Margery E.

It is incorrect to say "the test is reliable" because reliability is a function not only of the test itself, but of many factors. The present paper explains how different factors affect classical reliability estimates such as test-retest, interrater, internal consistency, and equivalent forms coefficients. Furthermore, the limits of classical test…

Validity and reliability of Optojump photoelectric cells for estimating vertical jump height.

PubMed

Glatthorn, Julia F; Gouge, Sylvain; Nussbaumer, Silvio; Stauffacher, Simone; Impellizzeri, Franco M; Maffiuletti, Nicola A

2011-02-01

Vertical jump is one of the most prevalent acts performed in several sport activities. It is therefore important to ensure that the measurements of vertical jump height made as a part of research or athlete support work have adequate validity and reliability. The aim of this study was to evaluate concurrent validity and reliability of the Optojump photocell system (Microgate, Bolzano, Italy) with force plate measurements for estimating vertical jump height. Twenty subjects were asked to perform maximal squat jumps and countermovement jumps, and flight time-derived jump heights obtained by the force plate were compared with those provided by Optojump, to examine its concurrent (criterion-related) validity (study 1). Twenty other subjects completed the same jump series on 2 different occasions (separated by 1 week), and jump heights of session 1 were compared with session 2, to investigate test-retest reliability of the Optojump system (study 2). Intraclass correlation coefficients (ICCs) for validity were very high (0.997-0.998), even if a systematic difference was consistently observed between force plate and Optojump (-1.06 cm; p < 0.001). Test-retest reliability of the Optojump system was excellent, with ICCs ranging from 0.982 to 0.989, low coefficients of variation (2.7%), and low random errors (±2.81 cm). The Optojump photocell system demonstrated strong concurrent validity and excellent test-retest reliability for the estimation of vertical jump height. We propose the following equation that allows force plate and Optojump results to be used interchangeably: force plate jump height (cm) = 1.02 × Optojump jump height + 0.29. In conclusion, the use of Optojump photoelectric cells is legitimate for field-based assessments of vertical jump height.

Processes and Procedures for Estimating Score Reliability and Precision

ERIC Educational Resources Information Center

Bardhoshi, Gerta; Erford, Bradley T.

2017-01-01

Precision is a key facet of test development, with score reliability determined primarily according to the types of error one wants to approximate and demonstrate. This article identifies and discusses several primary forms of reliability estimation: internal consistency (i.e., split-half, KR-20, a), test-retest, alternate forms, interscorer, and…

A Latent Class Approach to Estimating Test-Score Reliability

ERIC Educational Resources Information Center

van der Ark, L. Andries; van der Palm, Daniel W.; Sijtsma, Klaas

2011-01-01

This study presents a general framework for single-administration reliability methods, such as Cronbach's alpha, Guttman's lambda-2, and method MS. This general framework was used to derive a new approach to estimating test-score reliability by means of the unrestricted latent class model. This new approach is the latent class reliability…

Automation of reliability evaluation procedures through CARE - The computer-aided reliability estimation program.

NASA Technical Reports Server (NTRS)

Mathur, F. P.

1972-01-01

Description of an on-line interactive computer program called CARE (Computer-Aided Reliability Estimation) which can model self-repair and fault-tolerant organizations and perform certain other functions. Essentially CARE consists of a repository of mathematical equations defining the various basic redundancy schemes. These equations, under program control, are then interrelated to generate the desired mathematical model to fit the architecture of the system under evaluation. The mathematical model is then supplied with ground instances of its variables and is then evaluated to generate values for the reliability-theoretic functions applied to the model.

General Aviation Aircraft Reliability Study

NASA Technical Reports Server (NTRS)

Pettit, Duane; Turnbull, Andrew; Roelant, Henk A. (Technical Monitor)

2001-01-01

This reliability study was performed in order to provide the aviation community with an estimate of Complex General Aviation (GA) Aircraft System reliability. To successfully improve the safety and reliability for the next generation of GA aircraft, a study of current GA aircraft attributes was prudent. This was accomplished by benchmarking the reliability of operational Complex GA Aircraft Systems. Specifically, Complex GA Aircraft System reliability was estimated using data obtained from the logbooks of a random sample of the Complex GA Aircraft population.

The relationship between cost estimates reliability and BIM adoption: SEM analysis

NASA Astrophysics Data System (ADS)

Ismail, N. A. A.; Idris, N. H.; Ramli, H.; Rooshdi, R. R. Raja Muhammad; Sahamir, S. R.

2018-02-01

This paper presents the usage of Structural Equation Modelling (SEM) approach in analysing the effects of Building Information Modelling (BIM) technology adoption in improving the reliability of cost estimates. Based on the questionnaire survey results, SEM analysis using SPSS-AMOS application examined the relationships between BIM-improved information and cost estimates reliability factors, leading to BIM technology adoption. Six hypotheses were established prior to SEM analysis employing two types of SEM models, namely the Confirmatory Factor Analysis (CFA) model and full structural model. The SEM models were then validated through the assessment on their uni-dimensionality, validity, reliability, and fitness index, in line with the hypotheses tested. The final SEM model fit measures are: P-value=0.000, RMSEA=0.079<0.08, GFI=0.824, CFI=0.962>0.90, TLI=0.956>0.90, NFI=0.935>0.90 and ChiSq/df=2.259; indicating that the overall index values achieved the required level of model fitness. The model supports all the hypotheses evaluated, confirming that all relationship exists amongst the constructs are positive and significant. Ultimately, the analysis verified that most of the respondents foresee better understanding of project input information through BIM visualization, its reliable database and coordinated data, in developing more reliable cost estimates. They also perceive to accelerate their cost estimating task through BIM adoption.

Validity and reliability of central blood pressure estimated by upper arm oscillometric cuff pressure.

PubMed

Climie, Rachel E D; Schultz, Martin G; Nikolic, Sonja B; Ahuja, Kiran D K; Fell, James W; Sharman, James E

2012-04-01

Noninvasive central blood pressure (BP) independently predicts mortality, but current methods are operator-dependent, requiring skill to obtain quality recordings. The aims of this study were first, to determine the validity of an automatic, upper arm oscillometric cuff method for estimating central BP (O(CBP)) by comparison with the noninvasive reference standard of radial tonometry (T(CBP)). Second, we determined the intratest and intertest reliability of O(CBP). To assess validity, central BP was estimated by O(CBP) (Pulsecor R6.5B monitor) and compared with T(CBP) (SphygmoCor) in 47 participants free from cardiovascular disease (aged 57 ± 9 years) in supine, seated, and standing positions. Brachial mean arterial pressure (MAP) and diastolic BP (DBP) from the O(CBP) device were used to calibrate in both devices. Duplicate measures were recorded in each position on the same day to assess intratest reliability, and participants returned within 10 ± 7 days for repeat measurements to assess intertest reliability. There was a strong intraclass correlation (ICC = 0.987, P < 0.001) and small mean difference (1.2 ± 2.2 mm Hg) for central systolic BP (SBP) determined by O(CBP) compared with T(CBP). Ninety-six percent of all comparisons (n = 495 acceptable recordings) were within 5 mm Hg. With respect to reliability, there were strong correlations but higher limits of agreement for the intratest (ICC = 0.975, P < 0.001, mean difference 0.6 ± 4.5 mm Hg) and intertest (ICC = 0.895, P < 0.001, mean difference 4.3 ± 8.0 mm Hg) comparisons. Estimation of central SBP using cuff oscillometry is comparable to radial tonometry and has good reproducibility. As a noninvasive, relatively operator-independent method, O(CBP) may be as useful as T(CBP) for estimating central BP in clinical practice.

Evaluation of General Classes of Reliability Estimators Often Used in Statistical Analyses of Quasi-Experimental Designs

NASA Astrophysics Data System (ADS)

Saini, K. K.; Sehgal, R. K.; Sethi, B. L.

2008-10-01

In this paper major reliability estimators are analyzed and there comparatively result are discussed. There strengths and weaknesses are evaluated in this case study. Each of the reliability estimators has certain advantages and disadvantages. Inter-rater reliability is one of the best ways to estimate reliability when your measure is an observation. However, it requires multiple raters or observers. As an alternative, you could look at the correlation of ratings of the same single observer repeated on two different occasions. Each of the reliability estimators will give a different value for reliability. In general, the test-retest and inter-rater reliability estimates will be lower in value than the parallel forms and internal consistency ones because they involve measuring at different times or with different raters. Since reliability estimates are often used in statistical analyses of quasi-experimental designs.

How Many Sleep Diary Entries Are Needed to Reliably Estimate Adolescent Sleep?

PubMed Central

Arora, Teresa; Gradisar, Michael; Taheri, Shahrad; Carskadon, Mary A.

2017-01-01

Abstract Study Objectives: To investigate (1) how many nights of sleep diary entries are required for reliable estimates of five sleep-related outcomes (bedtime, wake time, sleep onset latency [SOL], sleep duration, and wake after sleep onset [WASO]) and (2) the test–retest reliability of sleep diary estimates of school night sleep across 12 weeks. Methods: Data were drawn from four adolescent samples (Australia [n = 385], Qatar [n = 245], United Kingdom [n = 770], and United States [n = 366]), who provided 1766 eligible sleep diary weeks for reliability analyses. We performed reliability analyses for each cohort using complete data (7 days), one to five school nights, and one to two weekend nights. We also performed test–retest reliability analyses on 12-week sleep diary data available from a subgroup of 55 US adolescents. Results: Intraclass correlation coefficients for bedtime, SOL, and sleep duration indicated good-to-excellent reliability from five weekday nights of sleep diary entries across all adolescent cohorts. Four school nights was sufficient for wake times in the Australian and UK samples, but not the US or Qatari samples. Only Australian adolescents showed good reliability for two weekend nights of bedtime reports; estimates of SOL were adequate for UK adolescents based on two weekend nights. WASO was not reliably estimated using 1 week of sleep diaries. We observed excellent test–rest reliability across 12 weeks of sleep diary data in a subsample of US adolescents. Conclusion: We recommend at least five weekday nights of sleep dairy entries to be made when studying adolescent bedtimes, SOL, and sleep duration. Adolescent sleep patterns were stable across 12 consecutive school weeks. PMID:28199718

A General Approach for Estimating Scale Score Reliability for Panel Survey Data

ERIC Educational Resources Information Center

Biemer, Paul P.; Christ, Sharon L.; Wiesen, Christopher A.

2009-01-01

Scale score measures are ubiquitous in the psychological literature and can be used as both dependent and independent variables in data analysis. Poor reliability of scale score measures leads to inflated standard errors and/or biased estimates, particularly in multivariate analysis. Reliability estimation is usually an integral step to assess…

User's guide to the Reliability Estimation System Testbed (REST)

NASA Technical Reports Server (NTRS)

Nicol, David M.; Palumbo, Daniel L.; Rifkin, Adam

1992-01-01

The Reliability Estimation System Testbed is an X-window based reliability modeling tool that was created to explore the use of the Reliability Modeling Language (RML). RML was defined to support several reliability analysis techniques including modularization, graphical representation, Failure Mode Effects Simulation (FMES), and parallel processing. These techniques are most useful in modeling large systems. Using modularization, an analyst can create reliability models for individual system components. The modules can be tested separately and then combined to compute the total system reliability. Because a one-to-one relationship can be established between system components and the reliability modules, a graphical user interface may be used to describe the system model. RML was designed to permit message passing between modules. This feature enables reliability modeling based on a run time simulation of the system wide effects of a component's failure modes. The use of failure modes effects simulation enhances the analyst's ability to correctly express system behavior when using the modularization approach to reliability modeling. To alleviate the computation bottleneck often found in large reliability models, REST was designed to take advantage of parallel processing on hypercube processors.

Reliability of Different Mark-Recapture Methods for Population Size Estimation Tested against Reference Population Sizes Constructed from Field Data

PubMed Central

Grimm, Annegret; Gruber, Bernd; Henle, Klaus

2014-01-01

Reliable estimates of population size are fundamental in many ecological studies and biodiversity conservation. Selecting appropriate methods to estimate abundance is often very difficult, especially if data are scarce. Most studies concerning the reliability of different estimators used simulation data based on assumptions about capture variability that do not necessarily reflect conditions in natural populations. Here, we used data from an intensively studied closed population of the arboreal gecko Gehyra variegata to construct reference population sizes for assessing twelve different population size estimators in terms of bias, precision, accuracy, and their 95%-confidence intervals. Two of the reference populations reflect natural biological entities, whereas the other reference populations reflect artificial subsets of the population. Since individual heterogeneity was assumed, we tested modifications of the Lincoln-Petersen estimator, a set of models in programs MARK and CARE-2, and a truncated geometric distribution. Ranking of methods was similar across criteria. Models accounting for individual heterogeneity performed best in all assessment criteria. For populations from heterogeneous habitats without obvious covariates explaining individual heterogeneity, we recommend using the moment estimator or the interpolated jackknife estimator (both implemented in CAPTURE/MARK). If data for capture frequencies are substantial, we recommend the sample coverage or the estimating equation (both models implemented in CARE-2). Depending on the distribution of catchabilities, our proposed multiple Lincoln-Petersen and a truncated geometric distribution obtained comparably good results. The former usually resulted in a minimum population size and the latter can be recommended when there is a long tail of low capture probabilities. Models with covariates and mixture models performed poorly. Our approach identified suitable methods and extended options to evaluate the

Estimates Of The Orbiter RSI Thermal Protection System Thermal Reliability

NASA Technical Reports Server (NTRS)

Kolodziej, P.; Rasky, D. J.

2002-01-01

In support of the Space Shuttle Orbiter post-flight inspection, structure temperatures are recorded at selected positions on the windward, leeward, starboard and port surfaces. Statistical analysis of this flight data and a non-dimensional load interference (NDLI) method are used to estimate the thermal reliability at positions were reusable surface insulation (RSI) is installed. In this analysis, structure temperatures that exceed the design limit define the critical failure mode. At thirty-three positions the RSI thermal reliability is greater than 0.999999 for the missions studied. This is not the overall system level reliability of the thermal protection system installed on an Orbiter. The results from two Orbiters, OV-102 and OV-105, are in good agreement. The original RSI designs on the OV-102 Orbital Maneuvering System pods, which had low reliability, were significantly improved on OV-105. The NDLI method was also used to estimate thermal reliability from an assessment of TPS uncertainties that was completed shortly before the first Orbiter flight. Results fiom the flight data analysis and the pre-flight assessment agree at several positions near each other. The NDLI method is also effective for optimizing RSI designs to provide uniform thermal reliability on the acreage surface of reusable launch vehicles.

How Many Sleep Diary Entries Are Needed to Reliably Estimate Adolescent Sleep?

PubMed

Short, Michelle A; Arora, Teresa; Gradisar, Michael; Taheri, Shahrad; Carskadon, Mary A

2017-03-01

To investigate (1) how many nights of sleep diary entries are required for reliable estimates of five sleep-related outcomes (bedtime, wake time, sleep onset latency [SOL], sleep duration, and wake after sleep onset [WASO]) and (2) the test-retest reliability of sleep diary estimates of school night sleep across 12 weeks. Data were drawn from four adolescent samples (Australia [n = 385], Qatar [n = 245], United Kingdom [n = 770], and United States [n = 366]), who provided 1766 eligible sleep diary weeks for reliability analyses. We performed reliability analyses for each cohort using complete data (7 days), one to five school nights, and one to two weekend nights. We also performed test-retest reliability analyses on 12-week sleep diary data available from a subgroup of 55 US adolescents. Intraclass correlation coefficients for bedtime, SOL, and sleep duration indicated good-to-excellent reliability from five weekday nights of sleep diary entries across all adolescent cohorts. Four school nights was sufficient for wake times in the Australian and UK samples, but not the US or Qatari samples. Only Australian adolescents showed good reliability for two weekend nights of bedtime reports; estimates of SOL were adequate for UK adolescents based on two weekend nights. WASO was not reliably estimated using 1 week of sleep diaries. We observed excellent test-rest reliability across 12 weeks of sleep diary data in a subsample of US adolescents. We recommend at least five weekday nights of sleep dairy entries to be made when studying adolescent bedtimes, SOL, and sleep duration. Adolescent sleep patterns were stable across 12 consecutive school weeks. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

A Reliability Estimation in Modeling Watershed Runoff With Uncertainties

NASA Astrophysics Data System (ADS)

Melching, Charles S.; Yen, Ben Chie; Wenzel, Harry G., Jr.

1990-10-01

The reliability of simulation results produced by watershed runoff models is a function of uncertainties in nature, data, model parameters, and model structure. A framework is presented here for using a reliability analysis method (such as first-order second-moment techniques or Monte Carlo simulation) to evaluate the combined effect of the uncertainties on the reliability of output hydrographs from hydrologic models. For a given event the prediction reliability can be expressed in terms of the probability distribution of the estimated hydrologic variable. The peak discharge probability for a watershed in Illinois using the HEC-1 watershed model is given as an example. The study of the reliability of predictions from watershed models provides useful information on the stochastic nature of output from deterministic models subject to uncertainties and identifies the relative contribution of the various uncertainties to unreliability of model predictions.

Reliability verification of vehicle speed estimate method in forensic videos.

PubMed

Kim, Jong-Hyuk; Oh, Won-Taek; Choi, Ji-Hun; Park, Jong-Chan

2018-06-01

In various types of traffic accidents, including car-to-car crash, vehicle-pedestrian collision, and hit-and-run accident, driver overspeed is one of the critical issues of traffic accident analysis. Hence, analysis of vehicle speed at the moment of accident is necessary. The present article proposes a vehicle speed estimate method (VSEM) applying a virtual plane and a virtual reference line to a forensic video. The reliability of the VSEM was verified by comparing the results obtained by applying the VSEM to videos from a test vehicle driving with a global positioning system (GPS)-based Vbox speed. The VSEM verified by these procedures was applied to real traffic accident examples to evaluate the usability of the VSEM. Copyright © 2018 Elsevier B.V. All rights reserved.

The first step toward genetic selection for host tolerance to infectious pathogens: obtaining the tolerance phenotype through group estimates

PubMed Central

Doeschl-Wilson, Andrea B.; Villanueva, Beatriz; Kyriazakis, Ilias

2012-01-01

Reliable phenotypes are paramount for meaningful quantification of genetic variation and for estimating individual breeding values on which genetic selection is based. In this paper, we assert that genetic improvement of host tolerance to disease, although desirable, may be first of all handicapped by the ability to obtain unbiased tolerance estimates at a phenotypic level. In contrast to resistance, which can be inferred by appropriate measures of within host pathogen burden, tolerance is more difficult to quantify as it refers to change in performance with respect to changes in pathogen burden. For this reason, tolerance phenotypes have only been specified at the level of a group of individuals, where such phenotypes can be estimated using regression analysis. However, few stsudies have raised the potential bias in these estimates resulting from confounding effects between resistance and tolerance. Using a simulation approach, we demonstrate (i) how these group tolerance estimates depend on within group variation and co-variation in resistance, tolerance, and vigor (performance in a pathogen free environment); and (ii) how tolerance estimates are affected by changes in pathogen virulence over the time course of infection and by the timing of measurements. We found that in order to obtain reliable group tolerance estimates, it is important to account for individual variation in vigor, if present, and that all individuals are at the same stage of infection when measurements are taken. The latter requirement makes estimation of tolerance based on cross-sectional field data challenging, as individuals become infected at different time points and the individual onset of infection is unknown. Repeated individual measurements of within host pathogen burden and performance would not only be valuable for inferring the infection status of individuals in field conditions, but would also provide tolerance estimates that capture the entire time course of infection. PMID

Use of NMR logging to obtain estimates of hydraulic conductivity in the High Plains aquifer, Nebraska, USA

USGS Publications Warehouse

Dlubac, Katherine; Knight, Rosemary; Song, Yi-Qiao; Bachman, Nate; Grau, Ben; Cannia, Jim; Williams, John

2013-01-01

Hydraulic conductivity (K) is one of the most important parameters of interest in groundwater applications because it quantifies the ease with which water can flow through an aquifer material. Hydraulic conductivity is typically measured by conducting aquifer tests or wellbore flow (WBF) logging. Of interest in our research is the use of proton nuclear magnetic resonance (NMR) logging to obtain information about water-filled porosity and pore space geometry, the combination of which can be used to estimate K. In this study, we acquired a suite of advanced geophysical logs, aquifer tests, WBF logs, and sidewall cores at the field site in Lexington, Nebraska, which is underlain by the High Plains aquifer. We first used two empirical equations developed for petroleum applications to predict K from NMR logging data: the Schlumberger Doll Research equation (KSDR) and the Timur-Coates equation (KT-C), with the standard empirical constants determined for consolidated materials. We upscaled our NMR-derived K estimates to the scale of the WBF-logging K(KWBF-logging) estimates for comparison. All the upscaled KT-C estimates were within an order of magnitude of KWBF-logging and all of the upscaled KSDR estimates were within 2 orders of magnitude of KWBF-logging. We optimized the fit between the upscaled NMR-derived K and KWBF-logging estimates to determine a set of site-specific empirical constants for the unconsolidated materials at our field site. We conclude that reliable estimates of K can be obtained from NMR logging data, thus providing an alternate method for obtaining estimates of K at high levels of vertical resolution.

Reliability and precision of pellet-group counts for estimating landscape-level deer density

Treesearch

David S. deCalesta

2013-01-01

This study provides hitherto unavailable methodology for reliably and precisely estimating deer density within forested landscapes, enabling quantitative rather than qualitative deer management. Reliability and precision of the deer pellet-group technique were evaluated in 1 small and 2 large forested landscapes. Density estimates, adjusted to reflect deer harvest and...

Inter-rater reliability of motor unit number estimates and quantitative motor unit analysis in the tibialis anterior muscle.

PubMed

Boe, S G; Dalton, B H; Harwood, B; Doherty, T J; Rice, C L

2009-05-01

To establish the inter-rater reliability of decomposition-based quantitative electromyography (DQEMG) derived motor unit number estimates (MUNEs) and quantitative motor unit (MU) analysis. Using DQEMG, two examiners independently obtained a sample of needle and surface-detected motor unit potentials (MUPs) from the tibialis anterior muscle from 10 subjects. Coupled with a maximal M wave, surface-detected MUPs were used to derive a MUNE for each subject and each examiner. Additionally, size-related parameters of the individual MUs were obtained following quantitative MUP analysis. Test-retest MUNE values were similar with high reliability observed between examiners (ICC=0.87). Additionally, MUNE variability from test-retest as quantified by a 95% confidence interval was relatively low (+/-28 MUs). Lastly, quantitative data pertaining to MU size, complexity and firing rate were similar between examiners. MUNEs and quantitative MU data can be obtained with high reliability by two independent examiners using DQEMG. Establishing the inter-rater reliability of MUNEs and quantitative MU analysis using DQEMG is central to the clinical applicability of the technique. In addition to assessing response to treatments over time, multiple clinicians may be involved in the longitudinal assessment of the MU pool of individuals with disorders of the central or peripheral nervous system.

Estimating Between-Person and Within-Person Subscore Reliability with Profile Analysis.

PubMed

Bulut, Okan; Davison, Mark L; Rodriguez, Michael C

2017-01-01

Subscores are of increasing interest in educational and psychological testing due to their diagnostic function for evaluating examinees' strengths and weaknesses within particular domains of knowledge. Previous studies about the utility of subscores have mostly focused on the overall reliability of individual subscores and ignored the fact that subscores should be distinct and have added value over the total score. This study introduces a profile reliability approach that partitions the overall subscore reliability into within-person and between-person subscore reliability. The estimation of between-person reliability and within-person reliability coefficients is demonstrated using subscores from number-correct scoring, unidimensional and multidimensional item response theory scoring, and augmented scoring approaches via a simulation study and a real data study. The effects of various testing conditions, such as subtest length, correlations among subscores, and the number of subtests, are examined. Results indicate that there is a substantial trade-off between within-person and between-person reliability of subscores. Profile reliability coefficients can be useful in determining the extent to which subscores provide distinct and reliable information under various testing conditions.

Reliability Estimation When a Test Is Split into Two Parts of Unknown Effective Length.

ERIC Educational Resources Information Center

Feldt, Leonard S.

2002-01-01

Considers the situation in which content or administrative considerations limit the way in which a test can be partitioned to estimate the internal consistency reliability of the total test score. Demonstrates that a single-valued estimate of the total score reliability is possible only if an assumption is made about the comparative size of the…

Portfolio assessment during medical internships: How to obtain a reliable and feasible assessment procedure?

PubMed

Michels, Nele R M; Driessen, Erik W; Muijtjens, Arno M M; Van Gaal, Luc F; Bossaert, Leo L; De Winter, Benedicte Y

2009-12-01

A portfolio is used to mentor and assess students' clinical performance at the workplace. However, students and raters often perceive the portfolio as a time-consuming instrument. In this study, we investigated whether assessment during medical internship by a portfolio can combine reliability and feasibility. The domain-oriented reliability of 61 double-rated portfolios was measured, using a generalisability analysis with portfolio tasks and raters as sources of variation in measuring the performance of a student. We obtained reliability (Phi coefficient) of 0.87 with this internship portfolio containing 15 double-rated tasks. The generalisability analysis showed that an acceptable level of reliability (Phi = 0.80) was maintained when the amount of portfolio tasks was decreased to 13 or 9 using one and two raters, respectively. Our study shows that a portfolio can be a reliable method for the assessment of workplace learning. The possibility of reducing the amount of tasks or raters while maintaining a sufficient level of reliability suggests an increase in feasibility of portfolio use for both students and raters.

Monte Carlo Approach for Reliability Estimations in Generalizability Studies.

ERIC Educational Resources Information Center

Dimitrov, Dimiter M.

A Monte Carlo approach is proposed, using the Statistical Analysis System (SAS) programming language, for estimating reliability coefficients in generalizability theory studies. Test scores are generated by a probabilistic model that considers the probability for a person with a given ability score to answer an item with a given difficulty…

A Laboratory Study on the Reliability Estimations of the Mini-CEX

ERIC Educational Resources Information Center

de Lima, Alberto Alves; Conde, Diego; Costabel, Juan; Corso, Juan; Van der Vleuten, Cees

2013-01-01

Reliability estimations of workplace-based assessments with the mini-CEX are typically based on real-life data. Estimations are based on the assumption of local independence: the object of the measurement should not be influenced by the measurement itself and samples should be completely independent. This is difficult to achieve. Furthermore, the…

Reliable estimation of orbit errors in spaceborne SAR interferometry. The network approach

NASA Astrophysics Data System (ADS)

Bähr, Hermann; Hanssen, Ramon F.

2012-12-01

An approach to improve orbital state vectors by orbit error estimates derived from residual phase patterns in synthetic aperture radar interferograms is presented. For individual interferograms, an error representation by two parameters is motivated: the baseline error in cross-range and the rate of change of the baseline error in range. For their estimation, two alternatives are proposed: a least squares approach that requires prior unwrapping and a less reliable gridsearch method handling the wrapped phase. In both cases, reliability is enhanced by mutual control of error estimates in an overdetermined network of linearly dependent interferometric combinations of images. Thus, systematic biases, e.g., due to unwrapping errors, can be detected and iteratively eliminated. Regularising the solution by a minimum-norm condition results in quasi-absolute orbit errors that refer to particular images. For the 31 images of a sample ENVISAT dataset, orbit corrections with a mutual consistency on the millimetre level have been inferred from 163 interferograms. The method itself qualifies by reliability and rigorous geometric modelling of the orbital error signal but does not consider interfering large scale deformation effects. However, a separation may be feasible in a combined processing with persistent scatterer approaches or by temporal filtering of the estimates.

Interval Estimation of Revision Effect on Scale Reliability via Covariance Structure Modeling

ERIC Educational Resources Information Center

Raykov, Tenko

2009-01-01

A didactic discussion of a procedure for interval estimation of change in scale reliability due to revision is provided, which is developed within the framework of covariance structure modeling. The method yields ranges of plausible values for the population gain or loss in reliability of unidimensional composites, which results from deletion or…

An iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions

NASA Technical Reports Server (NTRS)

Peters, B. C., Jr.; Walker, H. F.

1978-01-01

This paper addresses the problem of obtaining numerically maximum-likelihood estimates of the parameters for a mixture of normal distributions. In recent literature, a certain successive-approximations procedure, based on the likelihood equations, was shown empirically to be effective in numerically approximating such maximum-likelihood estimates; however, the reliability of this procedure was not established theoretically. Here, we introduce a general iterative procedure, of the generalized steepest-ascent (deflected-gradient) type, which is just the procedure known in the literature when the step-size is taken to be 1. We show that, with probability 1 as the sample size grows large, this procedure converges locally to the strongly consistent maximum-likelihood estimate whenever the step-size lies between 0 and 2. We also show that the step-size which yields optimal local convergence rates for large samples is determined in a sense by the 'separation' of the component normal densities and is bounded below by a number between 1 and 2.

Reliability of reflectance measures in passive filters

NASA Astrophysics Data System (ADS)

Saldiva de André, Carmen Diva; Afonso de André, Paulo; Rocha, Francisco Marcelo; Saldiva, Paulo Hilário Nascimento; Carvalho de Oliveira, Regiani; Singer, Julio M.

2014-08-01

Measurements of optical reflectance in passive filters impregnated with a reactive chemical solution may be transformed to ozone concentrations via a calibration curve and constitute a low cost alternative for environmental monitoring, mainly to estimate human exposure. Given the possibility of errors caused by exposure bias, it is common to consider sets of m filters exposed during a certain period to estimate the latent reflectance on n different sample occasions at a certain location. Mixed models with sample occasions as random effects are useful to analyze data obtained under such setups. The intra-class correlation coefficient of the mean of the m measurements is an indicator of the reliability of the latent reflectance estimates. Our objective is to determine m in order to obtain a pre-specified reliability of the estimates, taking possible outliers into account. To illustrate the procedure, we consider an experiment conducted at the Laboratory of Experimental Air Pollution, University of São Paulo, Brazil (LPAE/FMUSP), where sets of m = 3 filters were exposed during 7 days on n = 9 different occasions at a certain location. The results show that the reliability of the latent reflectance estimates for each occasion obtained under homoskedasticity is km = 0.74. A residual analysis suggests that the within-occasion variance for two of the occasions should be different from the others. A refined model with two within-occasion variance components was considered, yielding km = 0.56 for these occasions and km = 0.87 for the remaining ones. To guarantee that all estimates have a reliability of at least 80% we require measurements on m = 10 filters on each occasion.

Alternative Estimates of the Reliability of College Grade Point Averages. Professional File. Article 130, Spring 2013

ERIC Educational Resources Information Center

Saupe, Joe L.; Eimers, Mardy T.

2013-01-01

The purpose of this paper is to explore differences in the reliabilities of cumulative college grade point averages (GPAs), estimated for unweighted and weighted, one-semester, 1-year, 2-year, and 4-year GPAs. Using cumulative GPAs for a freshman class at a major university, we estimate internal consistency (coefficient alpha) reliabilities for…

An iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions, 2

NASA Technical Reports Server (NTRS)

Peters, B. C., Jr.; Walker, H. F.

1976-01-01

The problem of obtaining numerically maximum likelihood estimates of the parameters for a mixture of normal distributions is addressed. In recent literature, a certain successive approximations procedure, based on the likelihood equations, is shown empirically to be effective in numerically approximating such maximum-likelihood estimates; however, the reliability of this procedure was not established theoretically. Here, a general iterative procedure is introduced, of the generalized steepest-ascent (deflected-gradient) type, which is just the procedure known in the literature when the step-size is taken to be 1. With probability 1 as the sample size grows large, it is shown that this procedure converges locally to the strongly consistent maximum-likelihood estimate whenever the step-size lies between 0 and 2. The step-size which yields optimal local convergence rates for large samples is determined in a sense by the separation of the component normal densities and is bounded below by a number between 1 and 2.

A convenient method of obtaining percentile norms and accompanying interval estimates for self-report mood scales (DASS, DASS-21, HADS, PANAS, and sAD).

PubMed

Crawford, John R; Garthwaite, Paul H; Lawrie, Caroline J; Henry, Julie D; MacDonald, Marie A; Sutherland, Jane; Sinha, Priyanka

2009-06-01

A series of recent papers have reported normative data from the general adult population for commonly used self-report mood scales. To bring together and supplement these data in order to provide a convenient means of obtaining percentile norms for the mood scales. A computer program was developed that provides point and interval estimates of the percentile rank corresponding to raw scores on the various self-report scales. The program can be used to obtain point and interval estimates of the percentile rank of an individual's raw scores on the DASS, DASS-21, HADS, PANAS, and sAD mood scales, based on normative sample sizes ranging from 758 to 3822. The interval estimates can be obtained using either classical or Bayesian methods as preferred. The computer program (which can be downloaded at www.abdn.ac.uk/~psy086/dept/MoodScore.htm) provides a convenient and reliable means of supplementing existing cut-off scores for self-report mood scales.

Reliability of third molar development for age estimation in Gujarati population: A comparative study.

PubMed

Gandhi, Neha; Jain, Sandeep; Kumar, Manish; Rupakar, Pratik; Choyal, Kanaram; Prajapati, Seema

2015-01-01

Age assessment may be a crucial step in postmortem profiling leading to confirmative identification. In children, Demirjian's method based on eight developmental stages was developed to determine maturity scores as a function of age and polynomial functions to determine age as a function of score. Of this study was to evaluate the reliability of age estimation using Demirjian's eight teeth method following the French maturity scores and Indian-specific formula from developmental stages of third molar with the help of orthopantomograms using the Demirjian method. Dental panoramic tomograms from 30 subjects each of known chronological age and sex were collected and were evaluated according to Demirjian's criteria. Age calculations were performed using Demirjian's formula and Indian formula. Statistical analysis used was Chi-square test and ANOVA test and the P values obtained were statistically significant. There was an average underestimation of age with both Indian and Demirjian's formulas. The mean absolute error was lower using Indian formula hence it can be applied for age estimation in present Gujarati population. Also, females were ahead of achieving dental maturity than males thus completion of dental development is attained earlier in females. Greater accuracy can be obtained if population-specific formulas considering the ethnic and environmental variation are derived performing the regression analysis.

The reliability and validity of a three-camera foot image system for obtaining foot anthropometrics.

PubMed

O'Meara, Damien; Vanwanseele, Benedicte; Hunt, Adrienne; Smith, Richard

2010-08-01

The purpose was to develop a foot image capture and measurement system with web cameras (the 3-FIS) to provide reliable and valid foot anthropometric measures with efficiency comparable to that of the conventional method of using a handheld anthropometer. Eleven foot measures were obtained from 10 subjects using both methods. Reliability of each method was determined over 3 consecutive days using the intraclass correlation coefficient and root mean square error (RMSE). Reliability was excellent for both the 3-FIS and the handheld anthropometer for the same 10 variables, and good for the fifth metatarsophalangeal joint height. The RMSE values over 3 days ranged from 0.9 to 2.2 mm for the handheld anthropometer, and from 0.8 to 3.6 mm for the 3-FIS. The RMSE values between the 3-FIS and the handheld anthropometer were between 2.3 and 7.4 mm. The 3-FIS required less time to collect and obtain the final variables than the handheld anthropometer. The 3-FIS provided accurate and reproducible results for each of the foot variables and in less time than the conventional approach of a handheld anthropometer.

Reliability of Space-Shuttle Pressure Vessels with Random Batch Effects

NASA Technical Reports Server (NTRS)

Feiveson, Alan H.; Kulkarni, Pandurang M.

2000-01-01

In this article we revisit the problem of estimating the joint reliability against failure by stress rupture of a group of fiber-wrapped pressure vessels used on Space-Shuttle missions. The available test data were obtained from an experiment conducted at the U.S. Department of Energy Lawrence Livermore Laboratory (LLL) in which scaled-down vessels were subjected to life testing at four accelerated levels of pressure. We estimate the reliability assuming that both the Shuttle and LLL vessels were chosen at random in a two-stage process from an infinite population with spools of fiber as the primary sampling unit. Two main objectives of this work are: (1) to obtain practical estimates of reliability taking into account random spool effects and (2) to obtain a realistic assessment of estimation accuracy under the random model. Here, reliability is calculated in terms of a 'system' of 22 fiber-wrapped pressure vessels, taking into account typical pressures and exposure times experienced by Shuttle vessels. Comparisons are made with previous studies. The main conclusion of this study is that, although point estimates of reliability are still in the 'comfort zone,' it is advisable to plan for replacement of the pressure vessels well before the expected Lifetime of 100 missions per Shuttle Orbiter. Under a random-spool model, there is simply not enough information in the LLL data to provide reasonable assurance that such replacement would not be necessary.

Reliability of stellar inclination estimated from asteroseismology: analytical criteria, mock simulations and Kepler data analysis

NASA Astrophysics Data System (ADS)

Kamiaka, Shoya; Benomar, Othman; Suto, Yasushi

2018-05-01

Advances in asteroseismology of solar-like stars, now provide a unique method to estimate the stellar inclination i⋆. This enables to evaluate the spin-orbit angle of transiting planetary systems, in a complementary fashion to the Rossiter-McLaughlineffect, a well-established method to estimate the projected spin-orbit angle λ. Although the asteroseismic method has been broadly applied to the Kepler data, its reliability has yet to be assessed intensively. In this work, we evaluate the accuracy of i⋆ from asteroseismology of solar-like stars using 3000 simulated power spectra. We find that the low signal-to-noise ratio of the power spectra induces a systematic under-estimate (over-estimate) bias for stars with high (low) inclinations. We derive analytical criteria for the reliable asteroseismic estimate, which indicates that reliable measurements are possible in the range of 20° ≲ i⋆ ≲ 80° only for stars with high signal-to-noise ratio. We also analyse and measure the stellar inclination of 94 Kepler main-sequence solar-like stars, among which 33 are planetary hosts. According to our reliability criteria, a third of them (9 with planets, 22 without) have accurate stellar inclination. Comparison of our asteroseismic estimate of vsin i⋆ against spectroscopic measurements indicates that the latter suffers from a large uncertainty possibly due to the modeling of macro-turbulence, especially for stars with projected rotation speed vsin i⋆ ≲ 5km/s. This reinforces earlier claims, and the stellar inclination estimated from the combination of measurements from spectroscopy and photometric variation for slowly rotating stars needs to be interpreted with caution.

Estimation of reliability and dynamic property for polymeric material at high strain rate using SHPB technique and probability theory

NASA Astrophysics Data System (ADS)

Kim, Dong Hyeok; Lee, Ouk Sub; Kim, Hong Min; Choi, Hye Bin

2008-11-01

A modified Split Hopkinson Pressure Bar technique with aluminum pressure bars and a pulse shaper technique to achieve a closer impedance match between the pressure bars and the specimen materials such as hot temperature degraded POM (Poly Oxy Methylene) and PP (Poly Propylene). The more distinguishable experimental signals were obtained to evaluate the more accurate dynamic deformation behavior of materials under a high strain rate loading condition. A pulse shaping technique is introduced to reduce the non-equilibrium on the dynamic material response by modulation of the incident wave during a short period of test. This increases the rise time of the incident pulse in the SHPB experiment. For the dynamic stress strain curve obtained from SHPB experiment, the Johnson-Cook model is applied as a constitutive equation. The applicability of this constitutive equation is verified by using the probabilistic reliability estimation method. Two reliability methodologies such as the FORM and the SORM have been proposed. The limit state function(LSF) includes the Johnson-Cook model and applied stresses. The LSF in this study allows more statistical flexibility on the yield stress than a paper published before. It is found that the failure probability estimated by using the SORM is more reliable than those of the FORM/ It is also noted that the failure probability increases with increase of the applied stress. Moreover, it is also found that the parameters of Johnson-Cook model such as A and n, and the applied stress are found to affect the failure probability more severely than the other random variables according to the sensitivity analysis.

Validity and Reliability of Scores Obtained on Multiple-Choice Questions: Why Functioning Distractors Matter

ERIC Educational Resources Information Center

Ali, Syed Haris; Carr, Patrick A.; Ruit, Kenneth G.

2016-01-01

Plausible distractors are important for accurate measurement of knowledge via multiple-choice questions (MCQs). This study demonstrates the impact of higher distractor functioning on validity and reliability of scores obtained on MCQs. Freeresponse (FR) and MCQ versions of a neurohistology practice exam were given to four cohorts of Year 1 medical…

Validity and reliability of Nike + Fuelband for estimating physical activity energy expenditure.

PubMed

Tucker, Wesley J; Bhammar, Dharini M; Sawyer, Brandon J; Buman, Matthew P; Gaesser, Glenn A

2015-01-01

The Nike + Fuelband is a commercially available, wrist-worn accelerometer used to track physical activity energy expenditure (PAEE) during exercise. However, validation studies assessing the accuracy of this device for estimating PAEE are lacking. Therefore, this study examined the validity and reliability of the Nike + Fuelband for estimating PAEE during physical activity in young adults. Secondarily, we compared PAEE estimation of the Nike + Fuelband with the previously validated SenseWear Armband (SWA). Twenty-four participants (n = 24) completed two, 60-min semi-structured routines consisting of sedentary/light-intensity, moderate-intensity, and vigorous-intensity physical activity. Participants wore a Nike + Fuelband and SWA, while oxygen uptake was measured continuously with an Oxycon Mobile (OM) metabolic measurement system (criterion). The Nike + Fuelband (ICC = 0.77) and SWA (ICC = 0.61) both demonstrated moderate to good validity. PAEE estimates provided by the Nike + Fuelband (246 ± 67 kcal) and SWA (238 ± 57 kcal) were not statistically different than OM (243 ± 67 kcal). Both devices also displayed similar mean absolute percent errors for PAEE estimates (Nike + Fuelband = 16 ± 13 %; SWA = 18 ± 18 %). Test-retest reliability for PAEE indicated good stability for Nike + Fuelband (ICC = 0.96) and SWA (ICC = 0.90). The Nike + Fuelband provided valid and reliable estimates of PAEE, that are similar to the previously validated SWA, during a routine that included approximately equal amounts of sedentary/light-, moderate- and vigorous-intensity physical activity.

Reliability Estimation of Aero-engine Based on Mixed Weibull Distribution Model

NASA Astrophysics Data System (ADS)

Yuan, Zhongda; Deng, Junxiang; Wang, Dawei

2018-02-01

Aero-engine is a complex mechanical electronic system, based on analysis of reliability of mechanical electronic system, Weibull distribution model has an irreplaceable role. Till now, only two-parameter Weibull distribution model and three-parameter Weibull distribution are widely used. Due to diversity of engine failure modes, there is a big error with single Weibull distribution model. By contrast, a variety of engine failure modes can be taken into account with mixed Weibull distribution model, so it is a good statistical analysis model. Except the concept of dynamic weight coefficient, in order to make reliability estimation result more accurately, three-parameter correlation coefficient optimization method is applied to enhance Weibull distribution model, thus precision of mixed distribution reliability model is improved greatly. All of these are advantageous to popularize Weibull distribution model in engineering applications.

The Reliability of Difference Scores in Populations and Samples

ERIC Educational Resources Information Center

Zimmerman, Donald W.

2009-01-01

This study was an investigation of the relation between the reliability of difference scores, considered as a parameter characterizing a population of examinees, and the reliability estimates obtained from random samples from the population. The parameters in familiar equations for the reliability of difference scores were redefined in such a way…

The number of measurements needed to obtain high reliability for traits related to enzymatic activities and photosynthetic compounds in soybean plants infected with Phakopsora pachyrhizi.

PubMed

Oliveira, Tássia Boeno de; Azevedo Peixoto, Leonardo de; Teodoro, Paulo Eduardo; Alvarenga, Amauri Alves de; Bhering, Leonardo Lopes; Campo, Clara Beatriz Hoffmann

2018-01-01

Asian rust affects the physiology of soybean plants and causes losses in yield. Repeatability coefficients may help breeders to know how many measurements are needed to obtain a suitable reliability for a target trait. Therefore, the objectives of this study were to determine the repeatability coefficients of 14 traits in soybean plants inoculated with Phakopsora pachyrhizi and to establish the minimum number of measurements needed to predict the breeding value with high accuracy. Experiments were performed in a 3x2 factorial arrangement with three treatments and two inoculations in a random block design. Repeatability coefficients, coefficients of determination and number of measurements needed to obtain a certain reliability were estimated using ANOVA, principal component analysis based on the covariance matrix and the correlation matrix, structural analysis and mixed model. It was observed that the principal component analysis based on the covariance matrix out-performed other methods for almost all traits. Significant differences were observed for all traits except internal CO2 concentration for the treatment effects. For the measurement effects, all traits were significantly different. In addition, significant differences were found for all Treatment x Measurement interaction traits except coumestrol, chitinase and chlorophyll content. Six measurements were suitable to obtain a coefficient of determination higher than 0.7 for all traits based on principal component analysis. The information obtained from this research will help breeders and physiologists determine exactly how many measurements are needed to evaluate each trait in soybean plants infected by P. pachyrhizi with a desirable reliability.

The number of measurements needed to obtain high reliability for traits related to enzymatic activities and photosynthetic compounds in soybean plants infected with Phakopsora pachyrhizi

PubMed Central

de Oliveira, Tássia Boeno; Teodoro, Paulo Eduardo; de Alvarenga, Amauri Alves; Bhering, Leonardo Lopes; Campo, Clara Beatriz Hoffmann

2018-01-01

Asian rust affects the physiology of soybean plants and causes losses in yield. Repeatability coefficients may help breeders to know how many measurements are needed to obtain a suitable reliability for a target trait. Therefore, the objectives of this study were to determine the repeatability coefficients of 14 traits in soybean plants inoculated with Phakopsora pachyrhizi and to establish the minimum number of measurements needed to predict the breeding value with high accuracy. Experiments were performed in a 3x2 factorial arrangement with three treatments and two inoculations in a random block design. Repeatability coefficients, coefficients of determination and number of measurements needed to obtain a certain reliability were estimated using ANOVA, principal component analysis based on the covariance matrix and the correlation matrix, structural analysis and mixed model. It was observed that the principal component analysis based on the covariance matrix out-performed other methods for almost all traits. Significant differences were observed for all traits except internal CO2 concentration for the treatment effects. For the measurement effects, all traits were significantly different. In addition, significant differences were found for all Treatment x Measurement interaction traits except coumestrol, chitinase and chlorophyll content. Six measurements were suitable to obtain a coefficient of determination higher than 0.7 for all traits based on principal component analysis. The information obtained from this research will help breeders and physiologists determine exactly how many measurements are needed to evaluate each trait in soybean plants infected by P. pachyrhizi with a desirable reliability. PMID:29438380

A Note on the Reliability Coefficients for Item Response Model-Based Ability Estimates

ERIC Educational Resources Information Center

Kim, Seonghoon

2012-01-01

Assuming item parameters on a test are known constants, the reliability coefficient for item response theory (IRT) ability estimates is defined for a population of examinees in two different ways: as (a) the product-moment correlation between ability estimates on two parallel forms of a test and (b) the squared correlation between the true…

A Bayesian approach to parameter and reliability estimation in the Poisson distribution.

NASA Technical Reports Server (NTRS)

Canavos, G. C.

1972-01-01

For life testing procedures, a Bayesian analysis is developed with respect to a random intensity parameter in the Poisson distribution. Bayes estimators are derived for the Poisson parameter and the reliability function based on uniform and gamma prior distributions of that parameter. A Monte Carlo procedure is implemented to make possible an empirical mean-squared error comparison between Bayes and existing minimum variance unbiased, as well as maximum likelihood, estimators. As expected, the Bayes estimators have mean-squared errors that are appreciably smaller than those of the other two.

Probabilistic confidence for decisions based on uncertain reliability estimates

NASA Astrophysics Data System (ADS)

Reid, Stuart G.

2013-05-01

Reliability assessments are commonly carried out to provide a rational basis for risk-informed decisions concerning the design or maintenance of engineering systems and structures. However, calculated reliabilities and associated probabilities of failure often have significant uncertainties associated with the possible estimation errors relative to the 'true' failure probabilities. For uncertain probabilities of failure, a measure of 'probabilistic confidence' has been proposed to reflect the concern that uncertainty about the true probability of failure could result in a system or structure that is unsafe and could subsequently fail. The paper describes how the concept of probabilistic confidence can be applied to evaluate and appropriately limit the probabilities of failure attributable to particular uncertainties such as design errors that may critically affect the dependability of risk-acceptance decisions. This approach is illustrated with regard to the dependability of structural design processes based on prototype testing with uncertainties attributable to sampling variability.

Reliability of semiautomated computational methods for estimating tibiofemoral contact stress in the Multicenter Osteoarthritis Study.

PubMed

Anderson, Donald D; Segal, Neil A; Kern, Andrew M; Nevitt, Michael C; Torner, James C; Lynch, John A

2012-01-01

Recent findings suggest that contact stress is a potent predictor of subsequent symptomatic osteoarthritis development in the knee. However, much larger numbers of knees (likely on the order of hundreds, if not thousands) need to be reliably analyzed to achieve the statistical power necessary to clarify this relationship. This study assessed the reliability of new semiautomated computational methods for estimating contact stress in knees from large population-based cohorts. Ten knees of subjects from the Multicenter Osteoarthritis Study were included. Bone surfaces were manually segmented from sequential 1.0 Tesla magnetic resonance imaging slices by three individuals on two nonconsecutive days. Four individuals then registered the resulting bone surfaces to corresponding bone edges on weight-bearing radiographs, using a semi-automated algorithm. Discrete element analysis methods were used to estimate contact stress distributions for each knee. Segmentation and registration reliabilities (day-to-day and interrater) for peak and mean medial and lateral tibiofemoral contact stress were assessed with Shrout-Fleiss intraclass correlation coefficients (ICCs). The segmentation and registration steps of the modeling approach were found to have excellent day-to-day (ICC 0.93-0.99) and good inter-rater reliability (0.84-0.97). This approach for estimating compartment-specific tibiofemoral contact stress appears to be sufficiently reliable for use in large population-based cohorts.

The Riso-Hudson Enneagram Type Indicator: Estimates of Reliability and Validity

ERIC Educational Resources Information Center

Newgent, Rebecca A.; Parr, Patricia E.; Newman, Isadore; Higgins, Kristin K.

2004-01-01

This investigation was conducted to estimate the reliability and validity of scores on the Riso-Hudson Enneagram Type Indicator (D. R. Riso & R. Hudson, 1999a). Results of 287 participants were analyzed. Alpha suggests an adequate degree of internal consistency. Evidence provides mixed support for construct validity using correlational and…

Estimation of the KR20 Reliability Coefficient When Data Are Incomplete.

ERIC Educational Resources Information Center

Huynh, Huynh

Three techniques for estimating Kuder Richardson reliability (KR20) coefficients for incomplete data are contrasted. The methods are: (1) Henderson's Method 1 (analysis of variance, or ANOVA); (2) Henderson's Method 3 (FITCO); and (3) Koch's method of symmetric sums (SYSUM). A Monte Carlo simulation was used to assess the precision of the three…

Reliability of third molar development for age estimation in Gujarati population: A comparative study

PubMed Central

Gandhi, Neha; Jain, Sandeep; Kumar, Manish; Rupakar, Pratik; Choyal, Kanaram; Prajapati, Seema

2015-01-01

Background: Age assessment may be a crucial step in postmortem profiling leading to confirmative identification. In children, Demirjian's method based on eight developmental stages was developed to determine maturity scores as a function of age and polynomial functions to determine age as a function of score. Aim: Of this study was to evaluate the reliability of age estimation using Demirjian's eight teeth method following the French maturity scores and Indian-specific formula from developmental stages of third molar with the help of orthopantomograms using the Demirjian method. Materials and Methods: Dental panoramic tomograms from 30 subjects each of known chronological age and sex were collected and were evaluated according to Demirjian's criteria. Age calculations were performed using Demirjian's formula and Indian formula. Statistical analysis used was Chi-square test and ANOVA test and the P values obtained were statistically significant. Results: There was an average underestimation of age with both Indian and Demirjian's formulas. The mean absolute error was lower using Indian formula hence it can be applied for age estimation in present Gujarati population. Also, females were ahead of achieving dental maturity than males thus completion of dental development is attained earlier in females. Conclusion: Greater accuracy can be obtained if population-specific formulas considering the ethnic and environmental variation are derived performing the regression analysis. PMID:26005298

The reliability of Fishman method of skeletal maturation for age estimation in children of South Indian population

PubMed Central

Mohammed, Rezwana Begum; Kalyan, V. Siva; Tircouveluri, Saritha; Vegesna, Goutham Chakravarthy; Chirla, Anil; Varma, D. Maruthi

2014-01-01

Introduction: Determining the age of a person in the absence of documentary evidence of birth is essential for legal and medico-legal purpose. Fishman method of skeletal maturation is widely used for this purpose; however, the reliability of this method for people with all geographic locations is not well-established. Aims and Objectives: In this study, we assessed various stages of carpal and metacarpal bone maturation and tested the reliability of Fishman method of skeletal maturation to estimate the age in South Indian population. We also evaluated the correlation between the chronological age (CA) and predicted age based on the Fishman method of skeletal maturation. Materials and Methods: Digital right hand-wrist radiographs of 330 individuals aged 9-20 years were obtained and the skeletal maturity stage for each subject was determined using Fishman method. The skeletal maturation indicator scores were obtained and analyzed with reference to CA and sex. Data was analyzed using the SPSS software package (version 12, SPSS Inc., Chicago, IL, USA). Results: The study subjects had a tendency toward late maturation with the mean skeletal age (SA) estimated being significantly lowers (P < 0.05) than the mean CA at various skeletal maturity stages. Nevertheless, significant correlation was observed in this study between SA and CA for males (r = 0.82) and females (r = 0.85). Interestingly, female subjects were observed to be advanced in SA compared with males. Conclusion: Fishman method of skeletal maturation can be used as an alternative tool for the assessment of mean age of an individual of unknown CA in South Indian children. PMID:25097402

The reliability of Fishman method of skeletal maturation for age estimation in children of South Indian population.

PubMed

Mohammed, Rezwana Begum; Kalyan, V Siva; Tircouveluri, Saritha; Vegesna, Goutham Chakravarthy; Chirla, Anil; Varma, D Maruthi

2014-07-01

Determining the age of a person in the absence of documentary evidence of birth is essential for legal and medico-legal purpose. Fishman method of skeletal maturation is widely used for this purpose; however, the reliability of this method for people with all geographic locations is not well-established. In this study, we assessed various stages of carpal and metacarpal bone maturation and tested the reliability of Fishman method of skeletal maturation to estimate the age in South Indian population. We also evaluated the correlation between the chronological age (CA) and predicted age based on the Fishman method of skeletal maturation. Digital right hand-wrist radiographs of 330 individuals aged 9-20 years were obtained and the skeletal maturity stage for each subject was determined using Fishman method. The skeletal maturation indicator scores were obtained and analyzed with reference to CA and sex. Data was analyzed using the SPSS software package (version 12, SPSS Inc., Chicago, IL, USA). The study subjects had a tendency toward late maturation with the mean skeletal age (SA) estimated being significantly lowers (P < 0.05) than the mean CA at various skeletal maturity stages. Nevertheless, significant correlation was observed in this study between SA and CA for males (r = 0.82) and females (r = 0.85). Interestingly, female subjects were observed to be advanced in SA compared with males. Fishman method of skeletal maturation can be used as an alternative tool for the assessment of mean age of an individual of unknown CA in South Indian children.

Bayesian Estimation of Reliability Burr Type XII Under Al-Bayyatis’ Suggest Loss Function with Numerical Solution

NASA Astrophysics Data System (ADS)

Mohammed, Amal A.; Abraheem, Sudad K.; Fezaa Al-Obedy, Nadia J.

2018-05-01

In this paper is considered with Burr type XII distribution. The maximum likelihood, Bayes methods of estimation are used for estimating the unknown scale parameter (α). Al-Bayyatis’ loss function and suggest loss function are used to find the reliability with the least loss. So the reliability function is expanded in terms of a set of power function. For this performance, the Matlab (ver.9) is used in computations and some examples are given.

A time-frequency analysis method to obtain stable estimates of magnetotelluric response function based on Hilbert-Huang transform

NASA Astrophysics Data System (ADS)

Cai, Jianhua

2017-05-01

The time-frequency analysis method represents signal as a function of time and frequency, and it is considered a powerful tool for handling arbitrary non-stationary time series by using instantaneous frequency and instantaneous amplitude. It also provides a possible alternative to the analysis of the non-stationary magnetotelluric (MT) signal. Based on the Hilbert-Huang transform (HHT), a time-frequency analysis method is proposed to obtain stable estimates of the magnetotelluric response function. In contrast to conventional methods, the response function estimation is performed in the time-frequency domain using instantaneous spectra rather than in the frequency domain, which allows for imaging the response parameter content as a function of time and frequency. The theory of the method is presented and the mathematical model and calculation procedure, which are used to estimate response function based on HHT time-frequency spectrum, are discussed. To evaluate the results, response function estimates are compared with estimates from a standard MT data processing method based on the Fourier transform. All results show that apparent resistivities and phases, which are calculated from the HHT time-frequency method, are generally more stable and reliable than those determined from the simple Fourier analysis. The proposed method overcomes the drawbacks of the traditional Fourier methods, and the resulting parameter minimises the estimation bias caused by the non-stationary characteristics of the MT data.

Estimating the reliability of repeatedly measured endpoints based on linear mixed-effects models. A tutorial.

PubMed

Van der Elst, Wim; Molenberghs, Geert; Hilgers, Ralf-Dieter; Verbeke, Geert; Heussen, Nicole

2016-11-01

There are various settings in which researchers are interested in the assessment of the correlation between repeated measurements that are taken within the same subject (i.e., reliability). For example, the same rating scale may be used to assess the symptom severity of the same patients by multiple physicians, or the same outcome may be measured repeatedly over time in the same patients. Reliability can be estimated in various ways, for example, using the classical Pearson correlation or the intra-class correlation in clustered data. However, contemporary data often have a complex structure that goes well beyond the restrictive assumptions that are needed with the more conventional methods to estimate reliability. In the current paper, we propose a general and flexible modeling approach that allows for the derivation of reliability estimates, standard errors, and confidence intervals - appropriately taking hierarchies and covariates in the data into account. Our methodology is developed for continuous outcomes together with covariates of an arbitrary type. The methodology is illustrated in a case study, and a Web Appendix is provided which details the computations using the R package CorrMixed and the SAS software. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

The Reliability Estimation for the Open Function of Cabin Door Affected by the Imprecise Judgment Corresponding to Distribution Hypothesis

NASA Astrophysics Data System (ADS)

Yu, Z. P.; Yue, Z. F.; Liu, W.

2018-05-01

With the development of artificial intelligence, more and more reliability experts have noticed the roles of subjective information in the reliability design of complex system. Therefore, based on the certain numbers of experiment data and expert judgments, we have divided the reliability estimation based on distribution hypothesis into cognition process and reliability calculation. Consequently, for an illustration of this modification, we have taken the information fusion based on intuitional fuzzy belief functions as the diagnosis model of cognition process, and finished the reliability estimation for the open function of cabin door affected by the imprecise judgment corresponding to distribution hypothesis.

Expanding Reliability Generalization Methods with KR-21 Estimates: An RG Study of the Coopersmith Self-Esteem Inventory.

ERIC Educational Resources Information Center

Lane, Ginny G.; White, Amy E.; Henson, Robin K.

2002-01-01

Conducted a reliability generalizability study on the Coopersmith Self-Esteem Inventory (CSEI; S. Coopersmith, 1967) to examine the variability of reliability estimates across studies and to identify study characteristics that may predict this variability. Results show that reliability for CSEI scores can vary considerably, especially at the…

Evaluating North American Electric Grid Reliability Using the Barabasi-Albert Network Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chassin, David P.; Posse, Christian

2005-09-15

The reliability of electric transmission systems is examined using a scale-free model of network topology and failure propagation. The topologies of the North American eastern and western electric grids are analyzed to estimate their reliability based on the Barabási-Albert network model. A commonly used power system reliability index is computed using a simple failure propagation model. The results are compared to the values of power system reliability indices previously obtained using other methods and they suggest that scale-free network models are usable to estimate aggregate electric grid reliability.

Evaluating North American Electric Grid Reliability Using the Barabasi-Albert Network Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chassin, David P.; Posse, Christian

2005-09-15

The reliability of electric transmission systems is examined using a scale-free model of network topology and failure propagation. The topologies of the North American eastern and western electric grids are analyzed to estimate their reliability based on the Barabasi-Albert network model. A commonly used power system reliability index is computed using a simple failure propagation model. The results are compared to the values of power system reliability indices previously obtained using standard power engineering methods, and they suggest that scale-free network models are usable to estimate aggregate electric grid reliability.

Estimation of reliable range of electron temperature measurements with sets of given optical bandpass filters for KSTAR Thomson scattering system based on synthetic Thomson data

NASA Astrophysics Data System (ADS)

Kim, K.-h.; Oh, T.-s.; Park, K.-r.; Lee, J. H.; Ghim, Y.-c.

2017-11-01

One factor determining the reliability of measurements of electron temperature using a Thomson scattering (TS) system is transmittance of the optical bandpass filters in polychromators. We investigate the system performance as a function of electron temperature to determine reliable range of measurements for a given set of the optical bandpass filters. We show that such a reliability, i.e., both bias and random errors, can be obtained by building a forward model of the KSTAR TS system to generate synthetic TS data with the prescribed electron temperature and density profiles. The prescribed profiles are compared with the estimated ones to quantify both bias and random errors.

Reliability and Agreement in Student Ratings of the Class Environment

ERIC Educational Resources Information Center

Nelson, Peter M.; Christ, Theodore J.

2016-01-01

The current study estimated the reliability and agreement of student ratings of the classroom environment obtained using the Responsive Environmental Assessment for Classroom Teaching (REACT; Christ, Nelson, & Demers, 2012; Nelson, Demers, & Christ, 2014). Coefficient alpha, class-level reliability, and class agreement indices were…

Girsanov's transformation based variance reduced Monte Carlo simulation schemes for reliability estimation in nonlinear stochastic dynamics

NASA Astrophysics Data System (ADS)

Kanjilal, Oindrila; Manohar, C. S.

2017-07-01

The study considers the problem of simulation based time variant reliability analysis of nonlinear randomly excited dynamical systems. Attention is focused on importance sampling strategies based on the application of Girsanov's transformation method. Controls which minimize the distance function, as in the first order reliability method (FORM), are shown to minimize a bound on the sampling variance of the estimator for the probability of failure. Two schemes based on the application of calculus of variations for selecting control signals are proposed: the first obtains the control force as the solution of a two-point nonlinear boundary value problem, and, the second explores the application of the Volterra series in characterizing the controls. The relative merits of these schemes, vis-à-vis the method based on ideas from the FORM, are discussed. Illustrative examples, involving archetypal single degree of freedom (dof) nonlinear oscillators, and a multi-degree of freedom nonlinear dynamical system, are presented. The credentials of the proposed procedures are established by comparing the solutions with pertinent results from direct Monte Carlo simulations.

An Energy-Based Limit State Function for Estimation of Structural Reliability in Shock Environments

DOE PAGES

Guthrie, Michael A.

2013-01-01

limit state function is developed for the estimation of structural reliability in shock environments. This limit state function uses peak modal strain energies to characterize environmental severity and modal strain energies at failure to characterize the structural capacity. The Hasofer-Lind reliability index is briefly reviewed and its computation for the energy-based limit state function is discussed. Applications to two degree of freedom mass-spring systems and to a simple finite element model are considered. For these examples, computation of the reliability index requires little effort beyond a modal analysis, but still accounts for relevant uncertainties in both the structure and environment.more » For both examples, the reliability index is observed to agree well with the results of Monte Carlo analysis. In situations where fast, qualitative comparison of several candidate designs is required, the reliability index based on the proposed limit state function provides an attractive metric which can be used to compare and control reliability.« less

Estimation of gingival crevicular blood glucose level for the screening of diabetes mellitus: A simple yet reliable method.

PubMed

Parihar, Sarita; Tripathi, Richik; Parihar, Ajit Vikram; Samadi, Fahad M; Chandra, Akhilesh; Bhavsar, Neeta

2016-01-01

This study was designed to assess the reliability of blood glucose level estimation in gingival crevicular blood(GCB) for screening diabetes mellitus. 70 patients were included in study. A randomized, double-blind clinical trial was performed. Among these, 39 patients were diabetic (including 4 patients who were diagnosed during the study) and rest 31 patients were non-diabetic. GCB obtained during routine periodontal examination was analyzed by glucometer to know blood glucose level. The same patient underwent for finger stick blood (FSB) glucose level estimation with glucometer and venous blood (VB) glucose level with standardized laboratory method as per American Diabetes Association Guidelines. 1 All the three blood glucose levels were compared. Periodontal parameters were also recorded including gingival index (GI) and probing pocket depth (PPD). A strong positive correlation ( r ) was observed between glucose levels of GCB with FSB and VB with the values of 0.986 and 0.972 in diabetic group and 0.820 and 0.721 in non-diabetic group. As well, the mean values of GI and PPD were more in diabetic group than non-diabetic group with the statistically significant difference ( p  < 0.005). GCB can be reliably used to measure the blood glucose level as the values were closest to glucose levels estimated by VB. The technique is safe, easy to perform and non-invasive to the patient and can increase the frequency of diagnosing diabetes during routine periodontal therapy.

An Evaluation of Available Models for Estimating the Reliability and Validity of Criterion Referenced Measures.

ERIC Educational Resources Information Center

Oakland, Thomas

New strategies for evaluation criterion referenced measures (CRM) are discussed. These strategies examine the following issues: (1) the use of normed referenced measures (NRM) as CRM and then estimating the reliability and validity of such measures in terms of variance from an arbitrarily specified criterion score, (2) estimation of the…

Reliability based fatigue design and maintenance procedures

NASA Technical Reports Server (NTRS)

Hanagud, S.

1977-01-01

A stochastic model has been developed to describe a probability for fatigue process by assuming a varying hazard rate. This stochastic model can be used to obtain the desired probability of a crack of certain length at a given location after a certain number of cycles or time. Quantitative estimation of the developed model was also discussed. Application of the model to develop a procedure for reliability-based cost-effective fail-safe structural design is presented. This design procedure includes the reliability improvement due to inspection and repair. Methods of obtaining optimum inspection and maintenance schemes are treated.

Improving the quality of parameter estimates obtained from slug tests

USGS Publications Warehouse

Butler, J.J.; McElwee, C.D.; Liu, W.

1996-01-01

The slug test is one of the most commonly used field methods for obtaining in situ estimates of hydraulic conductivity. Despite its prevalence, this method has received criticism from many quarters in the ground-water community. This criticism emphasizes the poor quality of the estimated parameters, a condition that is primarily a product of the somewhat casual approach that is often employed in slug tests. Recently, the Kansas Geological Survey (KGS) has pursued research directed it improving methods for the performance and analysis of slug tests. Based on extensive theoretical and field research, a series of guidelines have been proposed that should enable the quality of parameter estimates to be improved. The most significant of these guidelines are: (1) three or more slug tests should be performed at each well during a given test period; (2) two or more different initial displacements (Ho) should be used at each well during a test period; (3) the method used to initiate a test should enable the slug to be introduced in a near-instantaneous manner and should allow a good estimate of Ho to be obtained; (4) data-acquisition equipment that enables a large quantity of high quality data to be collected should be employed; (5) if an estimate of the storage parameter is needed, an observation well other than the test well should be employed; (6) the method chosen for analysis of the slug-test data should be appropriate for site conditions; (7) use of pre- and post-analysis plots should be an integral component of the analysis procedure, and (8) appropriate well construction parameters should be employed. Data from slug tests performed at a number of KGS field sites demonstrate the importance of these guidelines.

Software analysis handbook: Software complexity analysis and software reliability estimation and prediction

NASA Technical Reports Server (NTRS)

Lee, Alice T.; Gunn, Todd; Pham, Tuan; Ricaldi, Ron

1994-01-01

This handbook documents the three software analysis processes the Space Station Software Analysis team uses to assess space station software, including their backgrounds, theories, tools, and analysis procedures. Potential applications of these analysis results are also presented. The first section describes how software complexity analysis provides quantitative information on code, such as code structure and risk areas, throughout the software life cycle. Software complexity analysis allows an analyst to understand the software structure, identify critical software components, assess risk areas within a software system, identify testing deficiencies, and recommend program improvements. Performing this type of analysis during the early design phases of software development can positively affect the process, and may prevent later, much larger, difficulties. The second section describes how software reliability estimation and prediction analysis, or software reliability, provides a quantitative means to measure the probability of failure-free operation of a computer program, and describes the two tools used by JSC to determine failure rates and design tradeoffs between reliability, costs, performance, and schedule.

Estimating Ordinal Reliability for Likert-Type and Ordinal Item Response Data: A Conceptual, Empirical, and Practical Guide

ERIC Educational Resources Information Center

Gadermann, Anne M.; Guhn, Martin; Zumbo, Bruno D.

2012-01-01

This paper provides a conceptual, empirical, and practical guide for estimating ordinal reliability coefficients for ordinal item response data (also referred to as Likert, Likert-type, ordered categorical, or rating scale item responses). Conventionally, reliability coefficients, such as Cronbach's alpha, are calculated using a Pearson…

On the Reliability of Source Time Functions Estimated Using Empirical Green's Function Methods

NASA Astrophysics Data System (ADS)

Gallegos, A. C.; Xie, J.; Suarez Salas, L.

2017-12-01

The Empirical Green's Function (EGF) method (Hartzell, 1978) has been widely used to extract source time functions (STFs). In this method, seismograms generated by collocated events with different magnitudes are deconvolved. Under a fundamental assumption that the STF of the small event is a delta function, the deconvolved Relative Source Time Function (RSTF) yields the large event's STF. While this assumption can be empirically justified by examination of differences in event size and frequency content of the seismograms, there can be a lack of rigorous justification of the assumption. In practice, a small event might have a finite duration when the RSTF is retrieved and interpreted as the large event STF with a bias. In this study, we rigorously analyze this bias using synthetic waveforms generated by convolving a realistic Green's function waveform with pairs of finite-duration triangular or parabolic STFs. The RSTFs are found using a time-domain based matrix deconvolution. We find when the STFs of smaller events are finite, the RSTFs are a series of narrow non-physical spikes. Interpreting these RSTFs as a series of high-frequency source radiations would be very misleading. The only reliable and unambiguous information we can retrieve from these RSTFs is the difference in durations and the moment ratio of the two STFs. We can apply a Tikhonov smoothing to obtain a single-pulse RSTF, but its duration is dependent on the choice of weighting, which may be subjective. We then test the Multi-Channel Deconvolution (MCD) method (Plourde & Bostock, 2017) which assumes that both STFs have finite durations to be solved for. A concern about the MCD method is that the number of unknown parameters is larger, which would tend to make the problem rank-deficient. Because the kernel matrix is dependent on the STFs to be solved for under a positivity constraint, we can only estimate the rank-deficiency with a semi-empirical approach. Based on the results so far, we find that the

Reliability of School Surveys in Estimating Geographic Variation in Malaria Transmission in the Western Kenyan Highlands

PubMed Central

Gitonga, Caroline W.; Gillig, Jonathan; Owaga, Chrispin; Marube, Elizabeth; Odongo, Wycliffe; Okoth, Albert; China, Pauline; Oriango, Robin; Brooker, Simon J.; Bousema, Teun; Drakeley, Chris; Cox, Jonathan

2013-01-01

Background School surveys provide an operational approach to assess malaria transmission through parasite prevalence. There is limited evidence on the comparability of prevalence estimates obtained from school and community surveys carried out at the same locality. Methods Concurrent school and community cross-sectional surveys were conducted in 46 school/community clusters in the western Kenyan highlands and households of school children were geolocated. Malaria was assessed by rapid diagnostic test (RDT) and combined seroprevalence of antibodies to bloodstage Plasmodium falciparum antigens. Results RDT prevalence in school and community populations was 25.7% (95% CI: 24.4-26.8) and 15.5% (95% CI: 14.4-16.7), respectively. Seroprevalence in the school and community populations was 51.9% (95% CI: 50.5-53.3) and 51.5% (95% CI: 49.5-52.9), respectively. RDT prevalence in schools could differentiate between low (<7%, 95% CI: 0-19%) and high (>39%, 95% CI: 25-49%) transmission areas in the community and, after a simple adjustment, were concordant with the community estimates. Conclusions Estimates of malaria prevalence from school surveys were consistently higher than those from community surveys and were strongly correlated. School-based estimates can be used as a reliable indicator of malaria transmission intensity in the wider community and may provide a basis for identifying priority areas for malaria control. PMID:24143250

Reliability estimation of a N- M-cold-standby redundancy system in a multicomponent stress-strength model with generalized half-logistic distribution

NASA Astrophysics Data System (ADS)

Liu, Yiming; Shi, Yimin; Bai, Xuchao; Zhan, Pei

2018-01-01

In this paper, we study the estimation for the reliability of a multicomponent system, named N- M-cold-standby redundancy system, based on progressive Type-II censoring sample. In the system, there are N subsystems consisting of M statistically independent distributed strength components, and only one of these subsystems works under the impact of stresses at a time and the others remain as standbys. Whenever the working subsystem fails, one from the standbys takes its place. The system fails when the entire subsystems fail. It is supposed that the underlying distributions of random strength and stress both belong to the generalized half-logistic distribution with different shape parameter. The reliability of the system is estimated by using both classical and Bayesian statistical inference. Uniformly minimum variance unbiased estimator and maximum likelihood estimator for the reliability of the system are derived. Under squared error loss function, the exact expression of the Bayes estimator for the reliability of the system is developed by using the Gauss hypergeometric function. The asymptotic confidence interval and corresponding coverage probabilities are derived based on both the Fisher and the observed information matrices. The approximate highest probability density credible interval is constructed by using Monte Carlo method. Monte Carlo simulations are performed to compare the performances of the proposed reliability estimators. A real data set is also analyzed for an illustration of the findings.

Reliability and comparison of Kinect-based methods for estimating spatiotemporal gait parameters of healthy and post-stroke individuals.

PubMed

Latorre, Jorge; Llorens, Roberto; Colomer, Carolina; Alcañiz, Mariano

2018-04-27

Different studies have analyzed the potential of the off-the-shelf Microsoft Kinect, in its different versions, to estimate spatiotemporal gait parameters as a portable markerless low-cost alternative to laboratory grade systems. However, variability in populations, measures, and methodologies prevents accurate comparison of the results. The objective of this study was to determine and compare the reliability of the existing Kinect-based methods to estimate spatiotemporal gait parameters in healthy and post-stroke adults. Forty-five healthy individuals and thirty-eight stroke survivors participated in this study. Participants walked five meters at a comfortable speed and their spatiotemporal gait parameters were estimated from the data retrieved by a Kinect v2, using the most common methods in the literature, and by visual inspection of the videotaped performance. Errors between both estimations were computed. For both healthy and post-stroke participants, highest accuracy was obtained when using the speed of the ankles to estimate gait speed (3.6-5.5 cm/s), stride length (2.5-5.5 cm), and stride time (about 45 ms), and when using the distance between the sacrum and the ankles and toes to estimate double support time (about 65 ms) and swing time (60-90 ms). Although the accuracy of these methods is limited, these measures could occasionally complement traditional tools. Copyright © 2018 Elsevier Ltd. All rights reserved.

Targeted estimation of nuisance parameters to obtain valid statistical inference.

PubMed

van der Laan, Mark J

2014-01-01

In order to obtain concrete results, we focus on estimation of the treatment specific mean, controlling for all measured baseline covariates, based on observing independent and identically distributed copies of a random variable consisting of baseline covariates, a subsequently assigned binary treatment, and a final outcome. The statistical model only assumes possible restrictions on the conditional distribution of treatment, given the covariates, the so-called propensity score. Estimators of the treatment specific mean involve estimation of the propensity score and/or estimation of the conditional mean of the outcome, given the treatment and covariates. In order to make these estimators asymptotically unbiased at any data distribution in the statistical model, it is essential to use data-adaptive estimators of these nuisance parameters such as ensemble learning, and specifically super-learning. Because such estimators involve optimal trade-off of bias and variance w.r.t. the infinite dimensional nuisance parameter itself, they result in a sub-optimal bias/variance trade-off for the resulting real-valued estimator of the estimand. We demonstrate that additional targeting of the estimators of these nuisance parameters guarantees that this bias for the estimand is second order and thereby allows us to prove theorems that establish asymptotic linearity of the estimator of the treatment specific mean under regularity conditions. These insights result in novel targeted minimum loss-based estimators (TMLEs) that use ensemble learning with additional targeted bias reduction to construct estimators of the nuisance parameters. In particular, we construct collaborative TMLEs (C-TMLEs) with known influence curve allowing for statistical inference, even though these C-TMLEs involve variable selection for the propensity score based on a criterion that measures how effective the resulting fit of the propensity score is in removing bias for the estimand. As a particular special

A Comparison of the Approaches of Generalizability Theory and Item Response Theory in Estimating the Reliability of Test Scores for Testlet-Composed Tests

ERIC Educational Resources Information Center

Lee, Guemin; Park, In-Yong

2012-01-01

Previous assessments of the reliability of test scores for testlet-composed tests have indicated that item-based estimation methods overestimate reliability. This study was designed to address issues related to the extent to which item-based estimation methods overestimate the reliability of test scores composed of testlets and to compare several…

Emulation applied to reliability analysis of reconfigurable, highly reliable, fault-tolerant computing systems

NASA Technical Reports Server (NTRS)

Migneault, G. E.

1979-01-01

Emulation techniques applied to the analysis of the reliability of highly reliable computer systems for future commercial aircraft are described. The lack of credible precision in reliability estimates obtained by analytical modeling techniques is first established. The difficulty is shown to be an unavoidable consequence of: (1) a high reliability requirement so demanding as to make system evaluation by use testing infeasible; (2) a complex system design technique, fault tolerance; (3) system reliability dominated by errors due to flaws in the system definition; and (4) elaborate analytical modeling techniques whose precision outputs are quite sensitive to errors of approximation in their input data. Next, the technique of emulation is described, indicating how its input is a simple description of the logical structure of a system and its output is the consequent behavior. Use of emulation techniques is discussed for pseudo-testing systems to evaluate bounds on the parameter values needed for the analytical techniques. Finally an illustrative example is presented to demonstrate from actual use the promise of the proposed application of emulation.

Assessing disease severity: accuracy and reliability of rater estimates in relation to number of diagrams in a standard area diagram set

USDA-ARS?s Scientific Manuscript database

Error in rater estimates of plant disease severity occur, and standard area diagrams (SADs) help improve accuracy and reliability. The effects of diagram number in a SAD set on accuracy and reliability is unknown. The objective of this study was to compare estimates of pecan scab severity made witho...

Evaluation Applied to Reliability Analysis of Reconfigurable, Highly Reliable, Fault-Tolerant, Computing Systems for Avionics

NASA Technical Reports Server (NTRS)

Migneault, G. E.

1979-01-01

Emulation techniques are proposed as a solution to a difficulty arising in the analysis of the reliability of highly reliable computer systems for future commercial aircraft. The difficulty, viz., the lack of credible precision in reliability estimates obtained by analytical modeling techniques are established. The difficulty is shown to be an unavoidable consequence of: (1) a high reliability requirement so demanding as to make system evaluation by use testing infeasible, (2) a complex system design technique, fault tolerance, (3) system reliability dominated by errors due to flaws in the system definition, and (4) elaborate analytical modeling techniques whose precision outputs are quite sensitive to errors of approximation in their input data. The technique of emulation is described, indicating how its input is a simple description of the logical structure of a system and its output is the consequent behavior. The use of emulation techniques is discussed for pseudo-testing systems to evaluate bounds on the parameter values needed for the analytical techniques.

Application of Stein and related parametric empirical Bayes estimators to the nuclear plant reliability data system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, J.R.; Heger, A.S.; Koen, B.V.

1984-04-01

This report is the result of a preliminary feasibility study of the applicability of Stein and related parametric empirical Bayes (PEB) estimators to the Nuclear Plant Reliability Data System (NPRDS). A new estimator is derived for the means of several independent Poisson distributions with different sampling times. This estimator is applied to data from NPRDS in an attempt to improve failure rate estimation. Theoretical and Monte Carlo results indicate that the new PEB estimator can perform significantly better than the standard maximum likelihood estimator if the estimation of the individual means can be combined through the loss function or throughmore » a parametric class of prior distributions.« less

Reliability of Scores Obtained from Self-, Peer-, and Teacher-Assessments on Teaching Materials Prepared by Teacher Candidates

ERIC Educational Resources Information Center

Nalbantoglu Yilmaz, Funda

2017-01-01

This study aims to determine the reliability of scores obtained from self-, peer-, and teacher-assessments in terms of teaching materials prepared by teacher candidates. The study group of this research constitutes 56 teacher candidates. In the scope of research, teacher candidates were asked to develop teaching material related to their study.…

Further assessment of a method to estimate reliability and validity of qualitative research findings.

PubMed

Hinds, P S; Scandrett-Hibden, S; McAulay, L S

1990-04-01

The reliability and validity of qualitative research findings are viewed with scepticism by some scientists. This scepticism is derived from the belief that qualitative researchers give insufficient attention to estimating reliability and validity of data, and the differences between quantitative and qualitative methods in assessing data. The danger of this scepticism is that relevant and applicable research findings will not be used. Our purpose is to describe an evaluative strategy for use with qualitative data, a strategy that is a synthesis of quantitative and qualitative assessment methods. Results of the strategy and factors that influence its use are also described.

Reliability Estimation for Single-unit Ceramic Crown Restorations

PubMed Central

Lekesiz, H.

2014-01-01

The objective of this study was to evaluate the potential of a survival prediction method for the assessment of ceramic dental restorations. For this purpose, fast-fracture and fatigue reliabilities for 2 bilayer (metal ceramic alloy core veneered with fluorapatite leucite glass-ceramic, d.Sign/d.Sign-67, by Ivoclar; glass-infiltrated alumina core veneered with feldspathic porcelain, VM7/In-Ceram Alumina, by Vita) and 3 monolithic (leucite-reinforced glass-ceramic, Empress, and ProCAD, by Ivoclar; lithium-disilicate glass-ceramic, Empress 2, by Ivoclar) single posterior crown restorations were predicted, and fatigue predictions were compared with the long-term clinical data presented in the literature. Both perfectly bonded and completely debonded cases were analyzed for evaluation of the influence of the adhesive/restoration bonding quality on estimations. Material constants and stress distributions required for predictions were calculated from biaxial tests and finite element analysis, respectively. Based on the predictions, In-Ceram Alumina presents the best fast-fracture resistance, and ProCAD presents a comparable resistance for perfect bonding; however, ProCAD shows a significant reduction of resistance in case of complete debonding. Nevertheless, it is still better than Empress and comparable with Empress 2. In-Ceram Alumina and d.Sign have the highest long-term reliability, with almost 100% survivability even after 10 years. When compared with clinical failure rates reported in the literature, predictions show a promising match with clinical data, and this indicates the soundness of the settings used in the proposed predictions. PMID:25048249

Ultrasound estimates of muscle quality in older adults: reliability and comparison of Photoshop and ImageJ for the grayscale analysis of muscle echogenicity

PubMed Central

Seamon, Bryant A.; Teixeira, Carla; Ismail, Catheeja

2016-01-01

Background. Quantitative diagnostic ultrasound imaging has been proposed as a method of estimating muscle quality using measures of echogenicity. The Rectangular Marquee Tool (RMT) and the Free Hand Tool (FHT) are two types of editing features used in Photoshop and ImageJ for determining a region of interest (ROI) within an ultrasound image. The primary objective of this study is to determine the intrarater and interrater reliability of Photoshop and ImageJ for the estimate of muscle tissue echogenicity in older adults via grayscale histogram analysis. The secondary objective is to compare the mean grayscale values obtained using both the RMT and FHT methods across both image analysis platforms. Methods. This cross-sectional observational study features 18 community-dwelling men (age = 61.5 ± 2.32 years). Longitudinal views of the rectus femoris were captured using B-mode ultrasound. The ROI for each scan was selected by 2 examiners using the RMT and FHT methods from each software program. Their reliability is assessed using intraclass correlation coefficients (ICCs) and the standard error of the measurement (SEM). Measurement agreement for these values is depicted using Bland-Altman plots. A paired t-test is used to determine mean differences in echogenicity expressed as grayscale values using the RMT and FHT methods to select the post-image acquisition ROI. The degree of association among ROI selection methods and image analysis platforms is analyzed using the coefficient of determination (R2). Results. The raters demonstrated excellent intrarater and interrater reliability using the RMT and FHT methods across both platforms (lower bound 95% CI ICC = .97–.99, p < .001). Mean differences between the echogenicity estimates obtained with the RMT and FHT methods was .87 grayscale levels (95% CI [.54–1.21], p < .0001) using data obtained with both programs. The SEM for Photoshop was .97 and 1.05 grayscale levels when using the RMT and FHT ROI selection methods

Development of a reliable estimation procedure of radioactivity inventory in a BWR plant due to neutron irradiation for decommissioning

NASA Astrophysics Data System (ADS)

Tanaka, Ken-ichi; Ueno, Jun

2017-09-01

Reliable information of radioactivity inventory resulted from the radiological characterization is important in order to plan decommissioning planning and is also crucial in order to promote decommissioning in effectiveness and in safe. The information is referred to by planning of decommissioning strategy and by an application to regulator. Reliable information of radioactivity inventory can be used to optimize the decommissioning processes. In order to perform the radiological characterization reliably, we improved a procedure of an evaluation of neutron-activated materials for a Boiling Water Reactor (BWR). Neutron-activated materials are calculated with calculation codes and their validity should be verified with measurements. The evaluation of neutron-activated materials can be divided into two processes. One is a distribution calculation of neutron-flux. Another is an activation calculation of materials. The distribution calculation of neutron-flux is performed with neutron transport calculation codes with appropriate cross section library to simulate neutron transport phenomena well. Using the distribution of neutron-flux, we perform distribution calculations of radioactivity concentration. We also estimate a time dependent distribution of radioactivity classification and a radioactive-waste classification. The information obtained from the evaluation is utilized by other tasks in the preparatory tasks to make the decommissioning plan and the activity safe and rational.

Timeline historical review of income and financial transactions: a reliable assessment of personal finances.

PubMed

Black, Anne C; Serowik, Kristin L; Ablondi, Karen M; Rosen, Marc I

2013-01-01

The need for accurate and reliable information about income and resources available to individuals with psychiatric disabilities is critical for the assessment of need and evaluation of programs designed to alleviate financial hardship or affect finance allocation. Measurement of finances is ubiquitous in studies of economics, poverty, and social services. However, evidence has demonstrated that these measures often contain error. We compare the 1-week test-retest reliability of income and finance data from 24 adult psychiatric outpatients using assessment-as-usual (AAU) and a new instrument, the Timeline Historical Review of Income and Financial Transactions (THRIFT). Reliability estimates obtained with the THRIFT for Income (0.77), Expenses (0.91), and Debt (0.99) domains were significantly better than those obtained with AAU. Reliability estimates for Balance did not differ. THRIFT reduced measurement error and provided more reliable information than AAU for assessment of personal finances in psychiatric patients receiving Social Security benefits. The instrument also may be useful with other low-income groups.

Reliability and validity of pendulum test measures of spasticity obtained with the Polhemus tracking system from patients with chronic stroke.

PubMed

Bohannon, Richard W; Harrison, Steven; Kinsella-Shaw, Jeffrey

2009-07-30

Spasticity is a common impairment accompanying stroke. Spasticity of the quadriceps femoris muscle can be quantified using the pendulum test. The measurement properties of pendular kinematics captured using a magnetic tracking system has not been studied among patients who have experienced a stroke. Therefore, this study describes the test-retest reliability and known groups and convergent validity of the pendulum test measures obtained with the Polhemus tracking system. Eight patients with chronic stroke underwent pendulum tests with their affected and unaffected lower limbs, with and without the addition of a 2.2 kg cuff weight at the ankle, using the Polhemus magnetic tracking system. Also measured bilaterally were knee resting angles, Ashworth scores (grades 0-4) of quadriceps femoris muscles, patellar tendon (knee jerk) reflexes (grades 0-4), and isometric knee extension force. Three measures obtained from pendular traces of the affected side were reliable (intraclass correlation coefficient > or = .844). Known groups validity was confirmed by demonstration of a significant difference in the measurements between sides. Convergent validity was supported by correlations > or = .57 between pendulum test measures and other measures reflective of spasticity. Pendulum test measures obtained with the Polhemus tracking system from the affected side of patients with stroke have good test-retest reliability and both known groups and convergent validity.

NMR permeability estimators in 'chalk' carbonate rocks obtained under different relaxation times and MICP size scalings

NASA Astrophysics Data System (ADS)

Rios, Edmilson Helton; Figueiredo, Irineu; Moss, Adam Keith; Pritchard, Timothy Neil; Glassborow, Brent Anthony; Guedes Domingues, Ana Beatriz; Bagueira de Vasconcellos Azeredo, Rodrigo

2016-07-01

The effect of the selection of different nuclear magnetic resonance (NMR) relaxation times for permeability estimation is investigated for a set of fully brine-saturated rocks acquired from Cretaceous carbonate reservoirs in the North Sea and Middle East. Estimators that are obtained from the relaxation times based on the Pythagorean means are compared with estimators that are obtained from the relaxation times based on the concept of a cumulative saturation cut-off. Select portions of the longitudinal (T1) and transverse (T2) relaxation-time distributions are systematically evaluated by applying various cut-offs, analogous to the Winland-Pittman approach for mercury injection capillary pressure (MICP) curves. Finally, different approaches to matching the NMR and MICP distributions using different mean-based scaling factors are validated based on the performance of the related size-scaled estimators. The good results that were obtained demonstrate possible alternatives to the commonly adopted logarithmic mean estimator and reinforce the importance of NMR-MICP integration to improving carbonate permeability estimates.

Comparing Fit and Reliability Estimates of a Psychological Instrument Using Second-Order CFA, Bifactor, and Essentially Tau-Equivalent (Coefficient Alpha) Models via AMOS 22

ERIC Educational Resources Information Center

Black, Ryan A.; Yang, Yanyun; Beitra, Danette; McCaffrey, Stacey

2015-01-01

Estimation of composite reliability within a hierarchical modeling framework has recently become of particular interest given the growing recognition that the underlying assumptions of coefficient alpha are often untenable. Unfortunately, coefficient alpha remains the prominent estimate of reliability when estimating total scores from a scale with…

Reliability of the measures of weight-bearing distribution obtained during quiet stance by digital scales in subjects with and without hemiparesis.

PubMed

de Araujo-Barbosa, Paulo Henrique Ferreira; de Menezes, Lidiane Teles; Costa, Abraão Souza; Couto Paz, Clarissa Cardoso Dos Santos; Fachin-Martins, Emerson

2015-05-01

Described as an alternative way of assessing weight-bearing asymmetries, the measures obtained from digital scales have been used as an index to classify weight-bearing distribution. This study aimed to describe the intra-test and the test/retest reliability of measures in subjects with and without hemiparesis during quiet stance. The percentage of body weight borne by one limb was calculated for a sample of subjects with hemiparesis and for a control group that was matched by gender and age. A two-way analysis of variance was used to verify the intra-test reliability. This analysis was calculated using the differences between the averages of the measures obtained during single, double or triple trials. The intra-class correlation coefficient (ICC) was utilized and data plotted using the Bland-Altman method. The intra-test analysis showed significant differences, only observed in the hemiparesis group, between the measures obtained by single and triple trials. Excellent and moderate ICC values (0.69-0.84) between test and retest were observed in the hemiparesis group, while for control groups ICC values (0.41-0.74) were classified as moderate, progressing from almost poor for measures obtained by a single trial to almost excellent for those obtained by triple trials. In conclusion, good reliability ranging from moderate to excellent classifications was found for participants with and without hemiparesis. Moreover, an improvement of the repeatability was observed with fewer trials for participants with hemiparesis, and with more trials for participants without hemiparesis.

Estimating the Reliability of Aggregated and Within-Person Centered Scores in Ecological Momentary Assessment

ERIC Educational Resources Information Center

Huang, Po-Hsien; Weng, Li-Jen

2012-01-01

A procedure for estimating the reliability of test scores in the context of ecological momentary assessment (EMA) was proposed to take into account the characteristics of EMA measures. Two commonly used test scores in EMA were considered: the aggregated score (AGGS) and the within-person centered score (WPCS). Conceptually, AGGS and WPCS represent…

Two Prophecy Formulas for Assessing the Reliability of Item Response Theory-Based Ability Estimates

ERIC Educational Resources Information Center

Raju, Nambury S.; Oshima, T.C.

2005-01-01

Two new prophecy formulas for estimating item response theory (IRT)-based reliability of a shortened or lengthened test are proposed. Some of the relationships between the two formulas, one of which is identical to the well-known Spearman-Brown prophecy formula, are examined and illustrated. The major assumptions underlying these formulas are…

MEASUREMENT: ACCOUNTING FOR RELIABILITY IN PERFORMANCE ESTIMATES.

PubMed

Waterman, Brian; Sutter, Robert; Burroughs, Thomas; Dunagan, W Claiborne

2014-01-01

When evaluating physician performance measures, physician leaders are faced with the quandary of determining whether departures from expected physician performance measurements represent a true signal or random error. This uncertainty impedes the physician leader's ability and confidence to take appropriate performance improvement actions based on physician performance measurements. Incorporating reliability adjustment into physician performance measurement is a valuable way of reducing the impact of random error in the measurements, such as those caused by small sample sizes. Consequently, the physician executive has more confidence that the results represent true performance and is positioned to make better physician performance improvement decisions. Applying reliability adjustment to physician-level performance data is relatively new. As others have noted previously, it's important to keep in mind that reliability adjustment adds significant complexity to the production, interpretation and utilization of results. Furthermore, the methods explored in this case study only scratch the surface of the range of available Bayesian methods that can be used for reliability adjustment; further study is needed to test and compare these methods in practice and to examine important extensions for handling specialty-specific concerns (e.g., average case volumes, which have been shown to be important in cardiac surgery outcomes). Moreover, it's important to note that the provider group average as a basis for shrinkage is one of several possible choices that could be employed in practice and deserves further exploration in future research. With these caveats, our results demonstrate that incorporating reliability adjustment into physician performance measurements is feasible and can notably reduce the incidence of "real" signals relative to what one would expect to see using more traditional approaches. A physician leader who is interested in catalyzing performance improvement

Validity and Reliability of Assessing Body Composition Using a Mobile Application.

PubMed

Macdonald, Elizabeth Z; Vehrs, Pat R; Fellingham, Gilbert W; Eggett, Dennis; George, James D; Hager, Ronald

2017-12-01

The purpose of this study was to determine the validity and reliability of the LeanScreen (LS) mobile application that estimates percent body fat (%BF) using estimates of circumferences from photographs. The %BF of 148 weight-stable adults was estimated once using dual-energy x-ray absorptiometry (DXA). Each of two administrators assessed the %BF of each subject twice using the LS app and manually measured circumferences. A mixed-model ANOVA and Bland-Altman analyses were used to compare the estimates of %BF obtained from each method. Interrater and intrarater reliabilities values were determined using multiple measurements taken by each of the two administrators. The LS app and manually measured circumferences significantly underestimated (P < 0.05) the %BF determined using DXA by an average of -3.26 and -4.82 %BF, respectively. The LS app (6.99 %BF) and manually measured circumferences (6.76 %BF) had large limits of agreement. All interrater and intrarater reliability coefficients of estimates of %BF using the LS app and manually measured circumferences exceeded 0.99. The estimates of %BF from manually measured circumferences and the LS app were highly reliable. However, these field measures are not currently recommended for the assessment of body composition because of significant bias and large limits of agreements.

Updated Value of Service Reliability Estimates for Electric Utility Customers in the United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sullivan, Michael; Schellenberg, Josh; Blundell, Marshall

2015-01-01

This report updates the 2009 meta-analysis that provides estimates of the value of service reliability for electricity customers in the United States (U.S.). The meta-dataset now includes 34 different datasets from surveys fielded by 10 different utility companies between 1989 and 2012. Because these studies used nearly identical interruption cost estimation or willingness-to-pay/accept methods, it was possible to integrate their results into a single meta-dataset describing the value of electric service reliability observed in all of them. Once the datasets from the various studies were combined, a two-part regression model was used to estimate customer damage functions that can bemore » generally applied to calculate customer interruption costs per event by season, time of day, day of week, and geographical regions within the U.S. for industrial, commercial, and residential customers. This report focuses on the backwards stepwise selection process that was used to develop the final revised model for all customer classes. Across customer classes, the revised customer interruption cost model has improved significantly because it incorporates more data and does not include the many extraneous variables that were in the original specification from the 2009 meta-analysis. The backwards stepwise selection process led to a more parsimonious model that only included key variables, while still achieving comparable out-of-sample predictive performance. In turn, users of interruption cost estimation tools such as the Interruption Cost Estimate (ICE) Calculator will have less customer characteristics information to provide and the associated inputs page will be far less cumbersome. The upcoming new version of the ICE Calculator is anticipated to be released in 2015.« less

Is biomass a reliable estimate of plant fitness?1

PubMed Central

Younginger, Brett S.; Sirová, Dagmara; Cruzan, Mitchell B.; Ballhorn, Daniel J.

2017-01-01

The measurement of fitness is critical to biological research. Although the determination of fitness for some organisms may be relatively straightforward under controlled conditions, it is often a difficult or nearly impossible task in nature. Plants are no exception. The potential for long-distance pollen dispersal, likelihood of multiple reproductive events per inflorescence, varying degrees of reproductive growth in perennials, and asexual reproduction all confound accurate fitness measurements. For these reasons, biomass is frequently used as a proxy for plant fitness. However, the suitability of indirect fitness measurements such as plant size is rarely evaluated. This review outlines the important associations between plant performance, fecundity, and fitness. We make a case for the reliability of biomass as an estimate of fitness when comparing conspecifics of the same age class. We reviewed 170 studies on plant fitness and discuss the metrics commonly employed for fitness estimations. We find that biomass or growth rate are frequently used and often positively associated with fecundity, which in turn suggests greater overall fitness. Our results support the utility of biomass as an appropriate surrogate for fitness under many circumstances, and suggest that additional fitness measures should be reported along with biomass or growth rate whenever possible. PMID:28224055

Reliability and validity of pendulum test measures of spasticity obtained with the Polhemus tracking system from patients with chronic stroke

PubMed Central

Bohannon, Richard W; Harrison, Steven; Kinsella-Shaw, Jeffrey

2009-01-01

Background Spasticity is a common impairment accompanying stroke. Spasticity of the quadriceps femoris muscle can be quantified using the pendulum test. The measurement properties of pendular kinematics captured using a magnetic tracking system has not been studied among patients who have experienced a stroke. Therefore, this study describes the test-retest reliability and known groups and convergent validity of the pendulum test measures obtained with the Polhemus tracking system. Methods Eight patients with chronic stroke underwent pendulum tests with their affected and unaffected lower limbs, with and without the addition of a 2.2 kg cuff weight at the ankle, using the Polhemus magnetic tracking system. Also measured bilaterally were knee resting angles, Ashworth scores (grades 0–4) of quadriceps femoris muscles, patellar tendon (knee jerk) reflexes (grades 0–4), and isometric knee extension force. Results Three measures obtained from pendular traces of the affected side were reliable (intraclass correlation coefficient ≥ .844). Known groups validity was confirmed by demonstration of a significant difference in the measurements between sides. Convergent validity was supported by correlations ≥ .57 between pendulum test measures and other measures reflective of spasticity. Conclusion Pendulum test measures obtained with the Polhemus tracking system from the affected side of patients with stroke have good test-retest reliability and both known groups and convergent validity. PMID:19642989

Reliability Impacts in Life Support Architecture and Technology Selection

NASA Technical Reports Server (NTRS)

Lange, Kevin E.; Anderson, Molly S.

2011-01-01

Equivalent System Mass (ESM) and reliability estimates were performed for different life support architectures based primarily on International Space Station (ISS) technologies. The analysis was applied to a hypothetical 1-year deep-space mission. High-level fault trees were initially developed relating loss of life support functionality to the Loss of Crew (LOC) top event. System reliability was then expressed as the complement (nonoccurrence) this event and was increased through the addition of redundancy and spares, which added to the ESM. The reliability analysis assumed constant failure rates and used current projected values of the Mean Time Between Failures (MTBF) from an ISS database where available. Results were obtained showing the dependence of ESM on system reliability for each architecture. Although the analysis employed numerous simplifications and many of the input parameters are considered to have high uncertainty, the results strongly suggest that achieving necessary reliabilities for deep-space missions will add substantially to the life support system mass. As a point of reference, the reliability for a single-string architecture using the most regenerative combination of ISS technologies without unscheduled replacement spares was estimated to be less than 1%. The results also demonstrate how adding technologies in a serial manner to increase system closure forces the reliability of other life support technologies to increase in order to meet the system reliability requirement. This increase in reliability results in increased mass for multiple technologies through the need for additional spares. Alternative parallel architecture approaches and approaches with the potential to do more with less are discussed. The tall poles in life support ESM are also reexamined in light of estimated reliability impacts.

Evaluating The Reliability of Point Estimates of Wetland Evaporation

NASA Astrophysics Data System (ADS)

Gavin, H.; Agnew, C. T.

The Penman-Monteith formulation of evaporation has been criticised for its reliance upon point estimates raising concerns that areal estimates of wetland evaporation based upon single weather stations can be misleading. Typically wetlands are composed of a complex mosaic of land cover types each of which can produce different evaporative rates. The need to account for wetland patches when monitoring hydrological fluxes has been noted, while Morton (1983) has long argued for a fundamentally different approach to the calculation of regional evaporation. This paper presents the work carried out at wet grassland in Southern England that was monitored with several automatic weather stations (AWS) and a bowen ratio station to investigate microclimate variations. The significance of fetch was examined using the approach adopted by Gash (1986) based upon surface roughness to estimate the fraction of evaporation sensed from a specific distance upwind of the monitoring station. This theoretical analysis reveals that the fraction of evaporation contributed by the surrounding area steadily increases to a value of 77% at a distance of 224m and thereafter declines rapidly, under stable atmospheric conditions. Thus point climate observations may not reflect surface conditions at greater distances. This result was tested through the deployment offour AWS around the wetland. The data yielded a different response, suggesting that homogeneous conditions prevailed and the central AWS did provide reliable areal estimates of evaporation. The apparent contradiction is a result of not accounting for wind speeds found in wetlands that lead to widespread atmospheric mixing. These findings are typical of moist conditions whereas for example Guo and Scheupp (1994) found that a patchwork of dry fields and wet ditches, characteristic of the study site in summer, could produce differences of up to 50% in evaporation. The paper will also present the initial results of an investigation of the role

Reliability and validity of Arabic Rapid Estimate of Adult Literacy in Dentistry (AREALD-30) in Saudi Arabia.

PubMed

Tadakamadla, Santosh Kumar; Quadri, Mir Faeq Ali; Pakpour, Amir H; Zailai, Abdulaziz M; Sayed, Mohammed E; Mashyakhy, Mohammed; Inamdar, Aadil S; Tadakamadla, Jyothi

2014-09-29

To evaluate the reliability and validity of Arabic Rapid Estimate of Adult Literacy in Dentistry (AREALD-30) in Saudi Arabia. A convenience sample of 200 subjects was approached, of which 177 agreed to participate giving a response rate of 88.5%. Rapid Estimate of Adult Literacy in Dentistry (REALD-99), was translated into Arabic to prepare the longer and shorter versions of Arabic Rapid Estimate of Adult Literacy in Dentistry (AREALD-99 and AREALD-30). Each participant was provided with AREALD-99 which also includes words from AREALD-30. A questionnaire containing socio-behavioral information and Arabic Oral Health Impact Profile (A-OHIP-14) was also administered. Reliability of the AREALD-30 was assessed by re-administering it to 20 subjects after two weeks. Convergent and predictive validity of AREALD-30 was evaluated by its correlations with AREALD-99 and self-perceived oral health status, dental visiting habits and A-OHIP-14 respectively. Discriminant validity was assessed in relation to the educational level while construct validity was evaluated by confirmatory factor analysis (CFA). Reliability of AREALD-30 was excellent with intraclass correlation coefficient of 0.99. It exhibited good convergent and discriminant validity but poor predictive validity. CFA showed presence of two factors and infit mean-square statistics for AREALD-30 were all within the desired range of 0.50 - 2.0 in Rasch analysis. AREALD-30 showed excellent reliability, good convergent and concurrent validity, but failed to predict the differences between the subjects categorized based on their oral health outcomes.

Estimating the Reliability of Single-Item Life Satisfaction Measures: Results from Four National Panel Studies

ERIC Educational Resources Information Center

Lucas, Richard E.; Donnellan, M. Brent

2012-01-01

Life satisfaction is often assessed using single-item measures. However, estimating the reliability of these measures can be difficult because internal consistency coefficients cannot be calculated. Existing approaches use longitudinal data to isolate occasion-specific variance from variance that is either completely stable or variance that…

Girsanov's transformation based variance reduced Monte Carlo simulation schemes for reliability estimation in nonlinear stochastic dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanjilal, Oindrila, E-mail: oindrila@civil.iisc.ernet.in; Manohar, C.S., E-mail: manohar@civil.iisc.ernet.in

The study considers the problem of simulation based time variant reliability analysis of nonlinear randomly excited dynamical systems. Attention is focused on importance sampling strategies based on the application of Girsanov's transformation method. Controls which minimize the distance function, as in the first order reliability method (FORM), are shown to minimize a bound on the sampling variance of the estimator for the probability of failure. Two schemes based on the application of calculus of variations for selecting control signals are proposed: the first obtains the control force as the solution of a two-point nonlinear boundary value problem, and, the secondmore » explores the application of the Volterra series in characterizing the controls. The relative merits of these schemes, vis-à-vis the method based on ideas from the FORM, are discussed. Illustrative examples, involving archetypal single degree of freedom (dof) nonlinear oscillators, and a multi-degree of freedom nonlinear dynamical system, are presented. The credentials of the proposed procedures are established by comparing the solutions with pertinent results from direct Monte Carlo simulations. - Highlights: • The distance minimizing control forces minimize a bound on the sampling variance. • Establishing Girsanov controls via solution of a two-point boundary value problem. • Girsanov controls via Volterra's series representation for the transfer functions.« less

Field reliability of competency and sanity opinions: A systematic review and meta-analysis.

PubMed

Guarnera, Lucy A; Murrie, Daniel C

2017-06-01

We know surprisingly little about the interrater reliability of forensic psychological opinions, even though courts and other authorities have long called for known error rates for scientific procedures admitted as courtroom testimony. This is particularly true for opinions produced during routine practice in the field, even for some of the most common types of forensic evaluations-evaluations of adjudicative competency and legal sanity. To address this gap, we used meta-analytic procedures and study space methodology to systematically review studies that examined the interrater reliability-particularly the field reliability-of competency and sanity opinions. Of 59 identified studies, 9 addressed the field reliability of competency opinions and 8 addressed the field reliability of sanity opinions. These studies presented a wide range of reliability estimates; pairwise percentage agreements ranged from 57% to 100% and kappas ranged from .28 to 1.0. Meta-analytic combinations of reliability estimates obtained by independent evaluators returned estimates of κ = .49 (95% CI: .40-.58) for competency opinions and κ = .41 (95% CI: .29-.53) for sanity opinions. This wide range of reliability estimates underscores the extent to which different evaluation contexts tend to produce different reliability rates. Unfortunately, our study space analysis illustrates that available field reliability studies typically provide little information about contextual variables crucial to understanding their findings. Given these concerns, we offer suggestions for improving research on the field reliability of competency and sanity opinions, as well as suggestions for improving reliability rates themselves. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Calculating system reliability with SRFYDO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morzinski, Jerome; Anderson - Cook, Christine M; Klamann, Richard M

2010-01-01

SRFYDO is a process for estimating reliability of complex systems. Using information from all applicable sources, including full-system (flight) data, component test data, and expert (engineering) judgment, SRFYDO produces reliability estimates and predictions. It is appropriate for series systems with possibly several versions of the system which share some common components. It models reliability as a function of age and up to 2 other lifecycle (usage) covariates. Initial output from its Exploratory Data Analysis mode consists of plots and numerical summaries so that the user can check data entry and model assumptions, and help determine a final form for themore » system model. The System Reliability mode runs a complete reliability calculation using Bayesian methodology. This mode produces results that estimate reliability at the component, sub-system, and system level. The results include estimates of uncertainty, and can predict reliability at some not-too-distant time in the future. This paper presents an overview of the underlying statistical model for the analysis, discusses model assumptions, and demonstrates usage of SRFYDO.« less

Reliability of functional and predictive methods to estimate the hip joint centre in human motion analysis in healthy adults.

PubMed

Kainz, Hans; Hajek, Martin; Modenese, Luca; Saxby, David J; Lloyd, David G; Carty, Christopher P

2017-03-01

In human motion analysis predictive or functional methods are used to estimate the location of the hip joint centre (HJC). It has been shown that the Harrington regression equations (HRE) and geometric sphere fit (GSF) method are the most accurate predictive and functional methods, respectively. To date, the comparative reliability of both approaches has not been assessed. The aims of this study were to (1) compare the reliability of the HRE and the GSF methods, (2) analyse the impact of the number of thigh markers used in the GSF method on the reliability, (3) evaluate how alterations to the movements that comprise the functional trials impact HJC estimations using the GSF method, and (4) assess the influence of the initial guess in the GSF method on the HJC estimation. Fourteen healthy adults were tested on two occasions using a three-dimensional motion capturing system. Skin surface marker positions were acquired while participants performed quite stance, perturbed and non-perturbed functional trials, and walking trials. Results showed that the HRE were more reliable in locating the HJC than the GSF method. However, comparison of inter-session hip kinematics during gait did not show any significant difference between the approaches. Different initial guesses in the GSF method did not result in significant differences in the final HJC location. The GSF method was sensitive to the functional trial performance and therefore it is important to standardize the functional trial performance to ensure a repeatable estimate of the HJC when using the GSF method. Copyright © 2017 Elsevier B.V. All rights reserved.

Reliability optimization design of the gear modification coefficient based on the meshing stiffness

NASA Astrophysics Data System (ADS)

Wang, Qianqian; Wang, Hui

2018-04-01

Since the time varying meshing stiffness of gear system is the key factor affecting gear vibration, it is important to design the meshing stiffness to reduce vibration. Based on the effect of gear modification coefficient on the meshing stiffness, considering the random parameters, reliability optimization design of the gear modification is researched. The dimension reduction and point estimation method is used to estimate the moment of the limit state function, and the reliability is obtained by the forth moment method. The cooperation of the dynamic amplitude results before and after optimization indicates that the research is useful for the reduction of vibration and noise and the improvement of the reliability.

Automatic training and reliability estimation for 3D ASM applied to cardiac MRI segmentation

NASA Astrophysics Data System (ADS)

Tobon-Gomez, Catalina; Sukno, Federico M.; Butakoff, Constantine; Huguet, Marina; Frangi, Alejandro F.

2012-07-01

Training active shape models requires collecting manual ground-truth meshes in a large image database. While shape information can be reused across multiple imaging modalities, intensity information needs to be imaging modality and protocol specific. In this context, this study has two main purposes: (1) to test the potential of using intensity models learned from MRI simulated datasets and (2) to test the potential of including a measure of reliability during the matching process to increase robustness. We used a population of 400 virtual subjects (XCAT phantom), and two clinical populations of 40 and 45 subjects. Virtual subjects were used to generate simulated datasets (MRISIM simulator). Intensity models were trained both on simulated and real datasets. The trained models were used to segment the left ventricle (LV) and right ventricle (RV) from real datasets. Segmentations were also obtained with and without reliability information. Performance was evaluated with point-to-surface and volume errors. Simulated intensity models obtained average accuracy comparable to inter-observer variability for LV segmentation. The inclusion of reliability information reduced volume errors in hypertrophic patients (EF errors from 17 ± 57% to 10 ± 18% LV MASS errors from -27 ± 22 g to -14 ± 25 g), and in heart failure patients (EF errors from -8 ± 42% to -5 ± 14%). The RV model of the simulated images needs further improvement to better resemble image intensities around the myocardial edges. Both for real and simulated models, reliability information increased segmentation robustness without penalizing accuracy.

Automatic training and reliability estimation for 3D ASM applied to cardiac MRI segmentation.

PubMed

Tobon-Gomez, Catalina; Sukno, Federico M; Butakoff, Constantine; Huguet, Marina; Frangi, Alejandro F

2012-07-07

Training active shape models requires collecting manual ground-truth meshes in a large image database. While shape information can be reused across multiple imaging modalities, intensity information needs to be imaging modality and protocol specific. In this context, this study has two main purposes: (1) to test the potential of using intensity models learned from MRI simulated datasets and (2) to test the potential of including a measure of reliability during the matching process to increase robustness. We used a population of 400 virtual subjects (XCAT phantom), and two clinical populations of 40 and 45 subjects. Virtual subjects were used to generate simulated datasets (MRISIM simulator). Intensity models were trained both on simulated and real datasets. The trained models were used to segment the left ventricle (LV) and right ventricle (RV) from real datasets. Segmentations were also obtained with and without reliability information. Performance was evaluated with point-to-surface and volume errors. Simulated intensity models obtained average accuracy comparable to inter-observer variability for LV segmentation. The inclusion of reliability information reduced volume errors in hypertrophic patients (EF errors from 17 ± 57% to 10 ± 18%; LV MASS errors from -27 ± 22 g to -14 ± 25 g), and in heart failure patients (EF errors from -8 ± 42% to -5 ± 14%). The RV model of the simulated images needs further improvement to better resemble image intensities around the myocardial edges. Both for real and simulated models, reliability information increased segmentation robustness without penalizing accuracy.

An experimental evaluation of software redundancy as a strategy for improving reliability

NASA Technical Reports Server (NTRS)

Eckhardt, Dave E., Jr.; Caglayan, Alper K.; Knight, John C.; Lee, Larry D.; Mcallister, David F.; Vouk, Mladen A.; Kelly, John P. J.

1990-01-01

The strategy of using multiple versions of independently developed software as a means to tolerate residual software design faults is suggested by the success of hardware redundancy for tolerating hardware failures. Although, as generally accepted, the independence of hardware failures resulting from physical wearout can lead to substantial increases in reliability for redundant hardware structures, a similar conclusion is not immediate for software. The degree to which design faults are manifested as independent failures determines the effectiveness of redundancy as a method for improving software reliability. Interest in multi-version software centers on whether it provides an adequate measure of increased reliability to warrant its use in critical applications. The effectiveness of multi-version software is studied by comparing estimates of the failure probabilities of these systems with the failure probabilities of single versions. The estimates are obtained under a model of dependent failures and compared with estimates obtained when failures are assumed to be independent. The experimental results are based on twenty versions of an aerospace application developed and certified by sixty programmers from four universities. Descriptions of the application, development and certification processes, and operational evaluation are given together with an analysis of the twenty versions.

Estimating sediment discharge: Appendix D

USGS Publications Warehouse

Gray, John R.; Simões, Francisco J. M.

2008-01-01

Sediment-discharge measurements usually are available on a discrete or periodic basis. However, estimates of sediment transport often are needed for unmeasured periods, such as when daily or annual sediment-discharge values are sought, or when estimates of transport rates for unmeasured or hypothetical flows are required. Selected methods for estimating suspended-sediment, bed-load, bed- material-load, and total-load discharges have been presented in some detail elsewhere in this volume. The purposes of this contribution are to present some limitations and potential pitfalls associated with obtaining and using the requisite data and equations to estimate sediment discharges and to provide guidance for selecting appropriate estimating equations. Records of sediment discharge are derived from data collected with sufficient frequency to obtain reliable estimates for the computational interval and period. Most sediment- discharge records are computed at daily or annual intervals based on periodically collected data, although some partial records represent discrete or seasonal intervals such as those for flood periods. The method used to calculate sediment- discharge records is dependent on the types and frequency of available data. Records for suspended-sediment discharge computed by methods described by Porterfield (1972) are most prevalent, in part because measurement protocols and computational techniques are well established and because suspended sediment composes the bulk of sediment dis- charges for many rivers. Discharge records for bed load, total load, or in some cases bed-material load plus wash load are less common. Reliable estimation of sediment discharges presupposes that the data on which the estimates are based are comparable and reliable. Unfortunately, data describing a selected characteristic of sediment were not necessarily derived—collected, processed, analyzed, or interpreted—in a consistent manner. For example, bed-load data collected with

Hardware and software reliability estimation using simulations

NASA Technical Reports Server (NTRS)

Swern, Frederic L.

1994-01-01

The simulation technique is used to explore the validation of both hardware and software. It was concluded that simulation is a viable means for validating both hardware and software and associating a reliability number with each. This is useful in determining the overall probability of system failure of an embedded processor unit, and improving both the code and the hardware where necessary to meet reliability requirements. The methodologies were proved using some simple programs, and simple hardware models.

Decoding tactile afferent activity to obtain an estimate of instantaneous force and torque applied to the fingerpad

PubMed Central

Birznieks, Ingvars; Redmond, Stephen J.

2015-01-01

Dexterous manipulation is not possible without sensory information about object properties and manipulative forces. Fundamental neuroscience has been unable to demonstrate how information about multiple stimulus parameters may be continuously extracted, concurrently, from a population of tactile afferents. This is the first study to demonstrate this, using spike trains recorded from tactile afferents innervating the monkey fingerpad. A multiple-regression model, requiring no a priori knowledge of stimulus-onset times or stimulus combination, was developed to obtain continuous estimates of instantaneous force and torque. The stimuli consisted of a normal-force ramp (to a plateau of 1.8, 2.2, or 2.5 N), on top of which −3.5, −2.0, 0, +2.0, or +3.5 mNm torque was applied about the normal to the skin surface. The model inputs were sliding windows of binned spike counts recorded from each afferent. Models were trained and tested by 15-fold cross-validation to estimate instantaneous normal force and torque over the entire stimulation period. With the use of the spike trains from 58 slow-adapting type I and 25 fast-adapting type I afferents, the instantaneous normal force and torque could be estimated with small error. This study demonstrated that instantaneous force and torque parameters could be reliably extracted from a small number of tactile afferent responses in a real-time fashion with stimulus combinations that the model had not been exposed to during training. Analysis of the model weights may reveal how interactions between stimulus parameters could be disentangled for complex population responses and could be used to test neurophysiologically relevant hypotheses about encoding mechanisms. PMID:25948866

Comparison of Sun-Induced Chlorophyll Fluorescence Estimates Obtained from Four Portable Field Spectroradiometers

NASA Technical Reports Server (NTRS)

Julitta, Tommaso; Corp, Lawrence A.; Rossini, Micol; Burkart, Andreas; Cogliati, Sergio; Davies, Neville; Hom, Milton; Mac Arthur, Alasdair; Middleton, Elizabeth M.; Rascher, Uwe;

Maximum likelihood estimation for predicting the probability of obtaining variable shortleaf pine regeneration densities

Treesearch

Thomas B. Lynch; Jean Nkouka; Michael M. Huebschmann; James M. Guldin

2003-01-01

A logistic equation is the basis for a model that predicts the probability of obtaining regeneration at specified densities. The density of regeneration (trees/ha) for which an estimate of probability is desired can be specified by means of independent variables in the model. When estimating parameters, the dependent variable is set to 1 if the regeneration density (...

Can a sample of Landsat sensor scenes reliably estimate the global extent of tropical deforestation?

Treesearch

R. L. Czaplewski

2003-01-01

Tucker and Townshend (2000) conclude that wall-to-wall coverage is needed to avoid gross errors in estimations of deforestation rates' because tropical deforestation is concentrated along roads and rivers. They specifically question the reliability of the 10% sample of Landsat sensor scenes used in the global remote sensing survey conducted by the Food and...

Neurology objective structured clinical examination reliability using generalizability theory

PubMed Central

Park, Yoon Soo; Lukas, Rimas V.; Brorson, James R.

2015-01-01

Objectives: This study examines factors affecting reliability, or consistency of assessment scores, from an objective structured clinical examination (OSCE) in neurology through generalizability theory (G theory). Methods: Data include assessments from a multistation OSCE taken by 194 medical students at the completion of a neurology clerkship. Facets evaluated in this study include cases, domains, and items. Domains refer to areas of skill (or constructs) that the OSCE measures. G theory is used to estimate variance components associated with each facet, derive reliability, and project the number of cases required to obtain a reliable (consistent, precise) score. Results: Reliability using G theory is moderate (Φ coefficient = 0.61, G coefficient = 0.64). Performance is similar across cases but differs by the particular domain, such that the majority of variance is attributed to the domain. Projections in reliability estimates reveal that students need to participate in 3 OSCE cases in order to increase reliability beyond the 0.70 threshold. Conclusions: This novel use of G theory in evaluating an OSCE in neurology provides meaningful measurement characteristics of the assessment. Differing from prior work in other medical specialties, the cases students were randomly assigned did not influence their OSCE score; rather, scores varied in expected fashion by domain assessed. PMID:26432851

Neurology objective structured clinical examination reliability using generalizability theory.

PubMed

Blood, Angela D; Park, Yoon Soo; Lukas, Rimas V; Brorson, James R

2015-11-03

This study examines factors affecting reliability, or consistency of assessment scores, from an objective structured clinical examination (OSCE) in neurology through generalizability theory (G theory). Data include assessments from a multistation OSCE taken by 194 medical students at the completion of a neurology clerkship. Facets evaluated in this study include cases, domains, and items. Domains refer to areas of skill (or constructs) that the OSCE measures. G theory is used to estimate variance components associated with each facet, derive reliability, and project the number of cases required to obtain a reliable (consistent, precise) score. Reliability using G theory is moderate (Φ coefficient = 0.61, G coefficient = 0.64). Performance is similar across cases but differs by the particular domain, such that the majority of variance is attributed to the domain. Projections in reliability estimates reveal that students need to participate in 3 OSCE cases in order to increase reliability beyond the 0.70 threshold. This novel use of G theory in evaluating an OSCE in neurology provides meaningful measurement characteristics of the assessment. Differing from prior work in other medical specialties, the cases students were randomly assigned did not influence their OSCE score; rather, scores varied in expected fashion by domain assessed. © 2015 American Academy of Neurology.

Reconciling Streamflow Uncertainty Estimation and River Bed Morphology Dynamics. Insights from a Probabilistic Assessment of Streamflow Uncertainties Using a Reliability Diagram

NASA Astrophysics Data System (ADS)

Morlot, T.; Mathevet, T.; Perret, C.; Favre Pugin, A. C.

2014-12-01

Streamflow uncertainty estimation has recently received a large attention in the literature. A dynamic rating curve assessment method has been introduced (Morlot et al., 2014). This dynamic method allows to compute a rating curve for each gauging and a continuous streamflow time-series, while calculating streamflow uncertainties. Streamflow uncertainty takes into account many sources of uncertainty (water level, rating curve interpolation and extrapolation, gauging aging, etc.) and produces an estimated distribution of streamflow for each days. In order to caracterise streamflow uncertainty, a probabilistic framework has been applied on a large sample of hydrometric stations of the Division Technique Générale (DTG) of Électricité de France (EDF) hydrometric network (>250 stations) in France. A reliability diagram (Wilks, 1995) has been constructed for some stations, based on the streamflow distribution estimated for a given day and compared to a real streamflow observation estimated via a gauging. To build a reliability diagram, we computed the probability of an observed streamflow (gauging), given the streamflow distribution. Then, the reliability diagram allows to check that the distribution of probabilities of non-exceedance of the gaugings follows a uniform law (i.e., quantiles should be equipropables). Given the shape of the reliability diagram, the probabilistic calibration is caracterised (underdispersion, overdispersion, bias) (Thyer et al., 2009). In this paper, we present case studies where reliability diagrams have different statistical properties for different periods. Compared to our knowledge of river bed morphology dynamic of these hydrometric stations, we show how reliability diagram gives us invaluable information on river bed movements, like a continuous digging or backfilling of the hydraulic control due to erosion or sedimentation processes. Hence, the careful analysis of reliability diagrams allows to reconcile statistics and long

Reverse lactate threshold: a novel single-session approach to reliable high-resolution estimation of the anaerobic threshold.

PubMed

Dotan, Raffy

2012-06-01

The multisession maximal lactate steady-state (MLSS) test is the gold standard for anaerobic threshold (AnT) estimation. However, it is highly impractical, requires high fitness level, and suffers additional shortcomings. Existing single-session AnT-estimating tests are of compromised validity, reliability, and resolution. The presented reverse lactate threshold test (RLT) is a single-session, AnT-estimating test, aimed at avoiding the pitfalls of existing tests. It is based on the novel concept of identifying blood lactate's maximal appearance-disappearance equilibrium by approaching the AnT from higher, rather than from lower exercise intensities. Rowing, cycling, and running case data (4 recreational and competitive athletes, male and female, aged 17-39 y) are presented. Subjects performed the RLT test and, on a separate session, a single 30-min MLSS-type verification test at the RLT-determined intensity. The RLT and its MLSS verification exhibited exceptional agreement at 0.5% discrepancy or better. The RLT's training sensitivity was demonstrated by a case of 2.5-mo training regimen following which the RLT's 15-W improvement was fully MLSS-verified. The RLT's test-retest reliability was examined in 10 trained and untrained subjects. Test 2 differed from test 1 by only 0.3% with an intraclass correlation of 0.997. The data suggest RLT to accurately and reliably estimate AnT (as represented by MLSS verification) with high resolution and in distinctly different sports and to be sensitive to training adaptations. Compared with MLSS, the single-session RLT is highly practical and its lower fitness requirements make it applicable to athletes and untrained individuals alike. Further research is needed to establish RLT's validity and accuracy in larger samples.

Hybrid time-variant reliability estimation for active control structures under aleatory and epistemic uncertainties

NASA Astrophysics Data System (ADS)

Wang, Lei; Xiong, Chuang; Wang, Xiaojun; Li, Yunlong; Xu, Menghui

2018-04-01

Considering that multi-source uncertainties from inherent nature as well as the external environment are unavoidable and severely affect the controller performance, the dynamic safety assessment with high confidence is of great significance for scientists and engineers. In view of this, the uncertainty quantification analysis and time-variant reliability estimation corresponding to the closed-loop control problems are conducted in this study under a mixture of random, interval, and convex uncertainties. By combining the state-space transformation and the natural set expansion, the boundary laws of controlled response histories are first confirmed with specific implementation of random items. For nonlinear cases, the collocation set methodology and fourth Rounge-Kutta algorithm are introduced as well. Enlightened by the first-passage model in random process theory as well as by the static probabilistic reliability ideas, a new definition of the hybrid time-variant reliability measurement is provided for the vibration control systems and the related solution details are further expounded. Two engineering examples are eventually presented to demonstrate the validity and applicability of the methodology developed.

Obtaining Cue Rate Estimates for Some Mysticete Species using Existing Data

DTIC Science & Technology

2014-09-30

primary focus is to obtain cue rates for humpback whales (Megaptera novaeangliae) off the California coast and on the PMRF range. To our knowledge, no... humpback whale cue rates have been calculated for these populations. Once a cue rate is estimated for the populations of humpback whales off the...rates for humpback whales on breeding grounds, in addition to average cue rates for other species of mysticete whales . Cue rates of several other

Software Reliability 2002

NASA Technical Reports Server (NTRS)

Wallace, Dolores R.

2003-01-01

In FY01 we learned that hardware reliability models need substantial changes to account for differences in software, thus making software reliability measurements more effective, accurate, and easier to apply. These reliability models are generally based on familiar distributions or parametric methods. An obvious question is 'What new statistical and probability models can be developed using non-parametric and distribution-free methods instead of the traditional parametric method?" Two approaches to software reliability engineering appear somewhat promising. The first study, begin in FY01, is based in hardware reliability, a very well established science that has many aspects that can be applied to software. This research effort has investigated mathematical aspects of hardware reliability and has identified those applicable to software. Currently the research effort is applying and testing these approaches to software reliability measurement, These parametric models require much project data that may be difficult to apply and interpret. Projects at GSFC are often complex in both technology and schedules. Assessing and estimating reliability of the final system is extremely difficult when various subsystems are tested and completed long before others. Parametric and distribution free techniques may offer a new and accurate way of modeling failure time and other project data to provide earlier and more accurate estimates of system reliability.

ERP Reliability Analysis (ERA) Toolbox: An open-source toolbox for analyzing the reliability of event-related brain potentials.

PubMed

Clayson, Peter E; Miller, Gregory A

2017-01-01

Generalizability theory (G theory) provides a flexible, multifaceted approach to estimating score reliability. G theory's approach to estimating score reliability has important advantages over classical test theory that are relevant for research using event-related brain potentials (ERPs). For example, G theory does not require parallel forms (i.e., equal means, variances, and covariances), can handle unbalanced designs, and provides a single reliability estimate for designs with multiple sources of error. This monograph provides a detailed description of the conceptual framework of G theory using examples relevant to ERP researchers, presents the algorithms needed to estimate ERP score reliability, and provides a detailed walkthrough of newly-developed software, the ERP Reliability Analysis (ERA) Toolbox, that calculates score reliability using G theory. The ERA Toolbox is open-source, Matlab software that uses G theory to estimate the contribution of the number of trials retained for averaging, group, and/or event types on ERP score reliability. The toolbox facilitates the rigorous evaluation of psychometric properties of ERP scores recommended elsewhere in this special issue. Copyright © 2016 Elsevier B.V. All rights reserved.

A fully redundant double difference algorithm for obtaining minimum variance estimates from GPS observations

NASA Technical Reports Server (NTRS)

Melbourne, William G.

1986-01-01

In double differencing a regression system obtained from concurrent Global Positioning System (GPS) observation sequences, one either undersamples the system to avoid introducing colored measurement statistics, or one fully samples the system incurring the resulting non-diagonal covariance matrix for the differenced measurement errors. A suboptimal estimation result will be obtained in the undersampling case and will also be obtained in the fully sampled case unless the color noise statistics are taken into account. The latter approach requires a least squares weighting matrix derived from inversion of a non-diagonal covariance matrix for the differenced measurement errors instead of inversion of the customary diagonal one associated with white noise processes. Presented is the so-called fully redundant double differencing algorithm for generating a weighted double differenced regression system that yields equivalent estimation results, but features for certain cases a diagonal weighting matrix even though the differenced measurement error statistics are highly colored.

Bayesian methods in reliability

NASA Astrophysics Data System (ADS)

Sander, P.; Badoux, R.

1991-11-01

The present proceedings from a course on Bayesian methods in reliability encompasses Bayesian statistical methods and their computational implementation, models for analyzing censored data from nonrepairable systems, the traits of repairable systems and growth models, the use of expert judgment, and a review of the problem of forecasting software reliability. Specific issues addressed include the use of Bayesian methods to estimate the leak rate of a gas pipeline, approximate analyses under great prior uncertainty, reliability estimation techniques, and a nonhomogeneous Poisson process. Also addressed are the calibration sets and seed variables of expert judgment systems for risk assessment, experimental illustrations of the use of expert judgment for reliability testing, and analyses of the predictive quality of software-reliability growth models such as the Weibull order statistics.

Bayes Error Rate Estimation Using Classifier Ensembles

NASA Technical Reports Server (NTRS)

Tumer, Kagan; Ghosh, Joydeep

2003-01-01

The Bayes error rate gives a statistical lower bound on the error achievable for a given classification problem and the associated choice of features. By reliably estimating th is rate, one can assess the usefulness of the feature set that is being used for classification. Moreover, by comparing the accuracy achieved by a given classifier with the Bayes rate, one can quantify how effective that classifier is. Classical approaches for estimating or finding bounds for the Bayes error, in general, yield rather weak results for small sample sizes; unless the problem has some simple characteristics, such as Gaussian class-conditional likelihoods. This article shows how the outputs of a classifier ensemble can be used to provide reliable and easily obtainable estimates of the Bayes error with negligible extra computation. Three methods of varying sophistication are described. First, we present a framework that estimates the Bayes error when multiple classifiers, each providing an estimate of the a posteriori class probabilities, a recombined through averaging. Second, we bolster this approach by adding an information theoretic measure of output correlation to the estimate. Finally, we discuss a more general method that just looks at the class labels indicated by ensem ble members and provides error estimates based on the disagreements among classifiers. The methods are illustrated for artificial data, a difficult four-class problem involving underwater acoustic data, and two problems from the Problem benchmarks. For data sets with known Bayes error, the combiner-based methods introduced in this article outperform existing methods. The estimates obtained by the proposed methods also seem quite reliable for the real-life data sets for which the true Bayes rates are unknown.

Validity and reliability of a food frequency questionnaire to estimate dietary intake among Lebanese children.

PubMed

Moghames, Patricia; Hammami, Nour; Hwalla, Nahla; Yazbeck, Nadine; Shoaib, Hikma; Nasreddine, Lara; Naja, Farah

2016-01-12

Nutritional status during childhood is critical given its effect on growth and development as well as its association with disease risk later in life. The Middle East and North Africa (MENA) region is experiencing alarming rates of childhood malnutrition, both over- and under-nutrition. Hence, there is a need for valid tools to assess dietary intake for children in this region. To date, there are no validated dietary assessment tools for children in any country of the MENA region. The main objective of this study was to examine the validity and reliability of a Food Frequency Questionnaire (FFQ) for the assessment of dietary intake among Lebanese children. Children, aged 5 to 10 years (n = 111), were recruited from public and private schools of Beirut, Lebanon. Mothers (proxies to report their children's dietary intake) completed two FFQs, four weeks apart. Four 24-hour recalls (24-HRs) were collected weekly during the duration of the study. Spearman correlations and Bland-Altman plots were used to assess validity. Linear regression models were used to derive calibration factors for boys and girls. Reproducibility statistics included Intraclass Correlation Coefficient (ICC) and percent agreement. Correlation coefficients between dietary intake estimates derived from FFQ and 24-HRs were significant at p < 0.001 with the highest correlation observed for energy (0.54) and the lowest for monounsaturated fatty acids (0.26). The majority of data points in the Bland-Altman plots lied between the limits of agreement, closer to the middle horizontal line. After applying the calibration factors for boys and girls, the mean energy and nutrient intakes estimated by the FFQ were similar to those obtained by the mean 24-HRs. As for reproducibility, ICC ranged between 0.31 for trans-fatty acids and 0.73 for calcium intakes. Over 80 % of study participants were classified in the same or adjacent quartile of energy and nutrients intake. Findings of this study showed that the

Probabilistic risk assessment for a loss of coolant accident in McMaster Nuclear Reactor and application of reliability physics model for modeling human reliability

NASA Astrophysics Data System (ADS)

Ha, Taesung

A probabilistic risk assessment (PRA) was conducted for a loss of coolant accident, (LOCA) in the McMaster Nuclear Reactor (MNR). A level 1 PRA was completed including event sequence modeling, system modeling, and quantification. To support the quantification of the accident sequence identified, data analysis using the Bayesian method and human reliability analysis (HRA) using the accident sequence evaluation procedure (ASEP) approach were performed. Since human performance in research reactors is significantly different from that in power reactors, a time-oriented HRA model (reliability physics model) was applied for the human error probability (HEP) estimation of the core relocation. This model is based on two competing random variables: phenomenological time and performance time. The response surface and direct Monte Carlo simulation with Latin Hypercube sampling were applied for estimating the phenomenological time, whereas the performance time was obtained from interviews with operators. An appropriate probability distribution for the phenomenological time was assigned by statistical goodness-of-fit tests. The human error probability (HEP) for the core relocation was estimated from these two competing quantities: phenomenological time and operators' performance time. The sensitivity of each probability distribution in human reliability estimation was investigated. In order to quantify the uncertainty in the predicted HEPs, a Bayesian approach was selected due to its capability of incorporating uncertainties in model itself and the parameters in that model. The HEP from the current time-oriented model was compared with that from the ASEP approach. Both results were used to evaluate the sensitivity of alternative huinan reliability modeling for the manual core relocation in the LOCA risk model. This exercise demonstrated the applicability of a reliability physics model supplemented with a. Bayesian approach for modeling human reliability and its potential

Between-day reliability of a method for non-invasive estimation of muscle composition.

PubMed

Simunič, Boštjan

2012-08-01

Tensiomyography is a method for valid and non-invasive estimation of skeletal muscle fibre type composition. The validity of selected temporal tensiomyographic measures has been well established recently; there is, however, no evidence regarding the method's between-day reliability. Therefore it is the aim of this paper to establish the between-day repeatability of tensiomyographic measures in three skeletal muscles. For three consecutive days, 10 healthy male volunteers (mean±SD: age 24.6 ± 3.0 years; height 177.9 ± 3.9 cm; weight 72.4 ± 5.2 kg) were examined in a supine position. Four temporal measures (delay, contraction, sustain, and half-relaxation time) and maximal amplitude were extracted from the displacement-time tensiomyogram. A reliability analysis was performed with calculations of bias, random error, coefficient of variation (CV), standard error of measurement, and intra-class correlation coefficient (ICC) with a 95% confidence interval. An analysis of ICC demonstrated excellent agreement (ICC were over 0.94 in 14 out of 15 tested parameters). However, lower CV was observed in half-relaxation time, presumably because of the specifics of the parameter definition itself. These data indicate that for the three muscles tested, tensiomyographic measurements were reproducible across consecutive test days. Furthermore, we indicated the most possible origin of the lowest reliability detected in half-relaxation time. Copyright © 2012 Elsevier Ltd. All rights reserved.

Multidisciplinary System Reliability Analysis

NASA Technical Reports Server (NTRS)

Mahadevan, Sankaran; Han, Song; Chamis, Christos C. (Technical Monitor)

2001-01-01

The objective of this study is to develop a new methodology for estimating the reliability of engineering systems that encompass multiple disciplines. The methodology is formulated in the context of the NESSUS probabilistic structural analysis code, developed under the leadership of NASA Glenn Research Center. The NESSUS code has been successfully applied to the reliability estimation of a variety of structural engineering systems. This study examines whether the features of NESSUS could be used to investigate the reliability of systems in other disciplines such as heat transfer, fluid mechanics, electrical circuits etc., without considerable programming effort specific to each discipline. In this study, the mechanical equivalence between system behavior models in different disciplines are investigated to achieve this objective. A new methodology is presented for the analysis of heat transfer, fluid flow, and electrical circuit problems using the structural analysis routines within NESSUS, by utilizing the equivalence between the computational quantities in different disciplines. This technique is integrated with the fast probability integration and system reliability techniques within the NESSUS code, to successfully compute the system reliability of multidisciplinary systems. Traditional as well as progressive failure analysis methods for system reliability estimation are demonstrated, through a numerical example of a heat exchanger system involving failure modes in structural, heat transfer and fluid flow disciplines.

Reliability and agreement in student ratings of the class environment.

PubMed

Nelson, Peter M; Christ, Theodore J

2016-09-01

The current study estimated the reliability and agreement of student ratings of the classroom environment obtained using the Responsive Environmental Assessment for Classroom Teaching (REACT; Christ, Nelson, & Demers, 2012; Nelson, Demers, & Christ, 2014). Coefficient alpha, class-level reliability, and class agreement indices were evaluated as each index provides important information for different interpretations and uses of student rating scale data. Data for 84 classes across 29 teachers in a suburban middle school were sampled to derive reliability and agreement indices for the REACT subscales across 4 class sizes: 25, 20, 15, and 10. All participating teachers were White and a larger number of 6th-grade classes were included (42%) relative to 7th- (33%) or 8th- (23%) grade classes. Teachers were responsible for a variety of content areas, including language arts (26%), science (26%), math (20%), social studies (19%), communications (6%), and Spanish (3%). Coefficient alpha estimates were generally high across all subscales and class sizes (α = .70-.95); class-mean estimates were greatly impacted by the number of students sampled from each class, with class-level reliability values generally falling below .70 when class size was reduced from 25 to 20. Further, within-class student agreement varied widely across the REACT subscales (mean agreement = .41-.80). Although coefficient alpha and test-retest reliability are commonly reported in research with student rating scales, class-level reliability and agreement are not. The observed differences across coefficient alpha, class-level reliability, and agreement indices provide evidence for evaluating students' ratings of the class environment according to their intended use (e.g., differentiating between classes, class-level instructional decisions). (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Reliability Stress-Strength Models for Dependent Observations with Applications in Clinical Trials

NASA Technical Reports Server (NTRS)

Kushary, Debashis; Kulkarni, Pandurang M.

1995-01-01

We consider the applications of stress-strength models in studies involving clinical trials. When studying the effects and side effects of certain procedures (treatments), it is often the case that observations are correlated due to subject effect, repeated measurements and observing many characteristics simultaneously. We develop maximum likelihood estimator (MLE) and uniform minimum variance unbiased estimator (UMVUE) of the reliability which in clinical trial studies could be considered as the chances of increased side effects due to a particular procedure compared to another. The results developed apply to both univariate and multivariate situations. Also, for the univariate situations we develop simple to use lower confidence bounds for the reliability. Further, we consider the cases when both stress and strength constitute time dependent processes. We define the future reliability and obtain methods of constructing lower confidence bounds for this reliability. Finally, we conduct simulation studies to evaluate all the procedures developed and also to compare the MLE and the UMVUE.

Reproducibility and interoperator reliability of obtaining images and measurements of the cervix and uterus with brachytherapy treatment applicators in situ using transabdominal ultrasound.

PubMed

van Dyk, Sylvia; Garth, Margaret; Oates, Amanda; Kondalsamy-Chennakesavan, Srinivas; Schneider, Michal; Bernshaw, David; Narayan, Kailash

2016-01-01

To validate interoperator reliability of brachytherapy radiation therapists (RTs) in obtaining an ultrasound image and measuring the cervix and uterine dimensions using transabdominal ultrasound. Patients who underwent MRI with applicators in situ after the first insertion were included in the study. Imaging was performed by three RTs (RT1, RT2, and RT3) with varying degrees of ultrasound experience. All RTs were required to obtain a longitudinal planning image depicting the applicator in the uterine canal and measure the cervix and uterus. The MRI scan, taken 1 hour after the ultrasound, was used as the reference standard against which all measurements were compared. Measurements were analyzed with intraclass correlation coefficient and Bland-Altman plots. All RTs were able to obtain a suitable longitudinal image for each patient in the study. Mean differences (SD) between MRI and ultrasound measurements obtained by RTs ranged from 3.5 (3.6) to 4.4 (4.23) mm and 0 (3.0) to 0.9 (2.5) mm on the anterior and posterior surface of the cervix, respectively. Intraclass correlation coefficient for absolute agreement between MRI and RTs was >0.9 for all posterior measurement points in the cervix and ranged from 0.41 to 0.92 on the anterior surface. Measurements were not statistically different between RTs at any measurement point. RTs with variable training attained high levels of interoperator reliability when using transabdominal ultrasound to obtain images and measurements of the uterus and cervix with brachytherapy applicators in situ. Access to training and use of a well-defined protocol assist in achieving these high levels of reliability. Copyright © 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Reliability Correction for Functional Connectivity: Theory and Implementation

PubMed Central

Mueller, Sophia; Wang, Danhong; Fox, Michael D.; Pan, Ruiqi; Lu, Jie; Li, Kuncheng; Sun, Wei; Buckner, Randy L.; Liu, Hesheng

2016-01-01

Network properties can be estimated using functional connectivity MRI (fcMRI). However, regional variation of the fMRI signal causes systematic biases in network estimates including correlation attenuation in regions of low measurement reliability. Here we computed the spatial distribution of fcMRI reliability using longitudinal fcMRI datasets and demonstrated how pre-estimated reliability maps can correct for correlation attenuation. As a test case of reliability-based attenuation correction we estimated properties of the default network, where reliability was significantly lower than average in the medial temporal lobe and higher in the posterior medial cortex, heterogeneity that impacts estimation of the network. Accounting for this bias using attenuation correction revealed that the medial temporal lobe’s contribution to the default network is typically underestimated. To render this approach useful to a greater number of datasets, we demonstrate that test-retest reliability maps derived from repeated runs within a single scanning session can be used as a surrogate for multi-session reliability mapping. Using data segments with different scan lengths between 1 and 30 min, we found that test-retest reliability of connectivity estimates increases with scan length while the spatial distribution of reliability is relatively stable even at short scan lengths. Finally, analyses of tertiary data revealed that reliability distribution is influenced by age, neuropsychiatric status and scanner type, suggesting that reliability correction may be especially important when studying between-group differences. Collectively, these results illustrate that reliability-based attenuation correction is an easily implemented strategy that mitigates certain features of fMRI signal nonuniformity. PMID:26493163

Reliability of Pain Measurements Using Computerized Cuff Algometry: A DoloCuff Reliability and Agreement Study.

PubMed

Kvistgaard Olsen, Jack; Fener, Dilay Kesgin; Waehrens, Eva Elisabet; Wulf Christensen, Anton; Jespersen, Anders; Danneskiold-Samsøe, Bente; Bartels, Else Marie

2017-07-01

Computerized pneumatic cuff pressure algometry (CPA) using the DoloCuff is a new method for pain assessment. Intra- and inter-rater reliabilities have not yet been established. Our aim was to examine the inter- and intrarater reliabilities of DoloCuff measures in healthy subjects. Twenty healthy subjects (ages 20 to 29 years) were assessed three times at 24-hour intervals by two trained raters. Inter-rater reliability was established based on the first and second assessments, whereas intrarater reliability was based on the second and third assessments. Subjects were randomized 1:1 to first assessment at either rater 1 or rater 2. The variables of interest were pressure pain threshold (PT), pressure pain tolerance (PTol), and temporal summation index (TSI). Reliability was estimated by a two-way mixed intraclass correlation coefficient (ICC) absolute agreement analysis. Reliability was considered excellent if ICC > 0.75, fair to good if 0.4 < ICC < 0.75, and poor if ICC < 0.4. Bias and random errors between raters and assessments were evaluated using 95% confidence interval (CI) and Bland-Altman plots. Inter-rater reliability for PT, PTol, and TSI was 0.88 (95% CI: 0.69 to 0.95), 0.86 (95% CI: 0.65 to 0.95), and 0.81 (95% CI: 0.42 to 0.94), respectively. The intrarater reliability for PT, PTol, and TSI was 0.81 (95% CI: 0.53 to 0.92), 0.89 (95% CI: 0.74 to 0.96), and 0.75 (95% CI: 0.28 to 0.91), respectively. Inter-rater reliability was excellent for PT, PTol, and TSI. Similarly, the intrarater reliability for PT and PTol was excellent, while borderline excellent/good for TSI. Therefore, the DoloCuff can be used to obtain reliable measures of pressure pain parameters in healthy subjects. © 2016 World Institute of Pain.

Estimating the Reliability of a Test Battery Composite or a Test Score Based on Weighted Item Scoring

ERIC Educational Resources Information Center

Feldt, Leonard S.

2004-01-01

In some settings, the validity of a battery composite or a test score is enhanced by weighting some parts or items more heavily than others in the total score. This article describes methods of estimating the total score reliability coefficient when differential weights are used with items or parts.

Can real time location system technology (RTLS) provide useful estimates of time use by nursing personnel?

PubMed

Jones, Terry L; Schlegel, Cara

2014-02-01

Accurate, precise, unbiased, reliable, and cost-effective estimates of nursing time use are needed to insure safe staffing levels. Direct observation of nurses is costly, and conventional surrogate measures have limitations. To test the potential of electronic capture of time and motion through real time location systems (RTLS), a pilot study was conducted to assess efficacy (method agreement) of RTLS time use; inter-rater reliability of RTLS time-use estimates; and associated costs. Method agreement was high (mean absolute difference = 28 seconds); inter-rater reliability was high (ICC = 0.81-0.95; mean absolute difference = 2 seconds); and costs for obtaining RTLS time-use estimates on a single nursing unit exceeded $25,000. Continued experimentation with RTLS to obtain time-use estimates for nursing staff is warranted. © 2013 Wiley Periodicals, Inc.

Parameter estimation techniques based on optimizing goodness-of-fit statistics for structural reliability

NASA Technical Reports Server (NTRS)

Starlinger, Alois; Duffy, Stephen F.; Palko, Joseph L.

1993-01-01

New methods are presented that utilize the optimization of goodness-of-fit statistics in order to estimate Weibull parameters from failure data. It is assumed that the underlying population is characterized by a three-parameter Weibull distribution. Goodness-of-fit tests are based on the empirical distribution function (EDF). The EDF is a step function, calculated using failure data, and represents an approximation of the cumulative distribution function for the underlying population. Statistics (such as the Kolmogorov-Smirnov statistic and the Anderson-Darling statistic) measure the discrepancy between the EDF and the cumulative distribution function (CDF). These statistics are minimized with respect to the three Weibull parameters. Due to nonlinearities encountered in the minimization process, Powell's numerical optimization procedure is applied to obtain the optimum value of the EDF. Numerical examples show the applicability of these new estimation methods. The results are compared to the estimates obtained with Cooper's nonlinear regression algorithm.

Software reliability perspectives

NASA Technical Reports Server (NTRS)

Wilson, Larry; Shen, Wenhui

1987-01-01

Software which is used in life critical functions must be known to be highly reliable before installation. This requires a strong testing program to estimate the reliability, since neither formal methods, software engineering nor fault tolerant methods can guarantee perfection. Prior to the final testing software goes through a debugging period and many models have been developed to try to estimate reliability from the debugging data. However, the existing models are poorly validated and often give poor performance. This paper emphasizes the fact that part of their failures can be attributed to the random nature of the debugging data given to these models as input, and it poses the problem of correcting this defect as an area of future research.

The reliability of in-training assessment when performance improvement is taken into account.

PubMed

van Lohuizen, Mirjam T; Kuks, Jan B M; van Hell, Elisabeth A; Raat, A N; Stewart, Roy E; Cohen-Schotanus, Janke

2010-12-01

During in-training assessment students are frequently assessed over a longer period of time and therefore it can be expected that their performance will improve. We studied whether there really is a measurable performance improvement when students are assessed over an extended period of time and how this improvement affects the reliability of the overall judgement. In-training assessment results were obtained from 104 students on rotation at our university hospital or at one of the six affiliated hospitals. Generalisability theory was used in combination with multilevel analysis to obtain reliability coefficients and to estimate the number of assessments needed for reliable overall judgement, both including and excluding performance improvement. Students' clinical performance ratings improved significantly from a mean of 7.6 at the start to a mean of 7.8 at the end of their clerkship. When taking performance improvement into account, reliability coefficients were higher. The number of assessments needed to achieve a reliability of 0.80 or higher decreased from 17 to 11. Therefore, when studying reliability of in-training assessment, performance improvement should be considered.

Test Reliability at the Individual Level

PubMed Central

Hu, Yueqin; Nesselroade, John R.; Erbacher, Monica K.; Boker, Steven M.; Burt, S. Alexandra; Keel, Pamela K.; Neale, Michael C.; Sisk, Cheryl L.; Klump, Kelly

2016-01-01

Reliability has a long history as one of the key psychometric properties of a test. However, a given test might not measure people equally reliably. Test scores from some individuals may have considerably greater error than others. This study proposed two approaches using intraindividual variation to estimate test reliability for each person. A simulation study suggested that the parallel tests approach and the structural equation modeling approach recovered the simulated reliability coefficients. Then in an empirical study, where forty-five females were measured daily on the Positive and Negative Affect Schedule (PANAS) for 45 consecutive days, separate estimates of reliability were generated for each person. Results showed that reliability estimates of the PANAS varied substantially from person to person. The methods provided in this article apply to tests measuring changeable attributes and require repeated measures across time on each individual. This article also provides a set of parallel forms of PANAS. PMID:28936107

The Examination of Reliability According to Classical Test and Generalizability on a Job Performance Scale

ERIC Educational Resources Information Center

Yelboga, Atilla; Tavsancil, Ezel

2010-01-01

In this research, the classical test theory and generalizability theory analyses were carried out with the data obtained by a job performance scale for the years 2005 and 2006. The reliability coefficients obtained (estimated) from the classical test theory and generalizability theory analyses were compared. In classical test theory, test retest…

Adaptive Reliable Routing Protocol Using Combined Link Stability Estimation for Mobile Ad hoc Networks

NASA Astrophysics Data System (ADS)

Vadivel, R.; Bhaskaran, V. Murali

2010-10-01

The main reason for packet loss in ad hoc networks is the link failure or node failure. In order to increase the path stability, it is essential to distinguish and moderate the failures. By knowing individual link stability along a path, path stability can be identified. In this paper, we develop an adaptive reliable routing protocol using combined link stability estimation for mobile ad hoc networks. The main objective of this protocol is to determine a Quality of Service (QoS) path along with prolonging the network life time and to reduce the packet loss. We calculate a combined metric for a path based on the parameters Link Expiration Time, Node Remaining Energy and Node Velocity and received signal strength to predict the link stability or lifetime. Then, a bypass route is established to retransmit the lost data, when a link failure occurs. By simulation results, we show that the proposed reliable routing protocol achieves high delivery ratio with reduced delay and packet drop.

Towards reliable ET estimates in the semi-arid Júcar region in Spain.

NASA Astrophysics Data System (ADS)

Brenner, Johannes; Zink, Matthias; Schrön, Martin; Thober, Stephan; Rakovec, Oldrich; Cuntz, Matthias; Merz, Ralf; Samaniego, Luis

2017-04-01

yields in poor performance in streamflow. Results suggest the need of multi-variable, simultaneous calibration schemes to reliable estimate ET and streamflow in the Júcar basin. Penman-Montheith appears to be the best performing PET formulation. Experiments 4 and 5 should reveal the benefits of separating evaporation from bare soil and transpiration in semi-arid regions using mHM. Further research in this direction is foreseen by incorporating neutron counts from Cosmic Ray Neutron Sensing technology in the calibration/validation procedure of mHM.

Probabilities and statistics for backscatter estimates obtained by a scatterometer with applications to new scatterometer design data

NASA Technical Reports Server (NTRS)

Pierson, Willard J., Jr.

1989-01-01

The values of the Normalized Radar Backscattering Cross Section (NRCS), sigma (o), obtained by a scatterometer are random variables whose variance is a known function of the expected value. The probability density function can be obtained from the normal distribution. Models for the expected value obtain it as a function of the properties of the waves on the ocean and the winds that generated the waves. Point estimates of the expected value were found from various statistics given the parameters that define the probability density function for each value. Random intervals were derived with a preassigned probability of containing that value. A statistical test to determine whether or not successive values of sigma (o) are truly independent was derived. The maximum likelihood estimates for wind speed and direction were found, given a model for backscatter as a function of the properties of the waves on the ocean. These estimates are biased as a result of the terms in the equation that involve natural logarithms, and calculations of the point estimates of the maximum likelihood values are used to show that the contributions of the logarithmic terms are negligible and that the terms can be omitted.

Stress Rupture Life Reliability Measures for Composite Overwrapped Pressure Vessels

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.; Thesken, John C.; Phoenix, S. Leigh; Grimes-Ledesma, Lorie

2007-01-01

Composite Overwrapped Pressure Vessels (COPVs) are often used for storing pressurant gases onboard spacecraft. Kevlar (DuPont), glass, carbon and other more recent fibers have all been used as overwraps. Due to the fact that overwraps are subjected to sustained loads for an extended period during a mission, stress rupture failure is a major concern. It is therefore important to ascertain the reliability of these vessels by analysis, since the testing of each flight design cannot be completed on a practical time scale. The present paper examines specifically a Weibull statistics based stress rupture model and considers the various uncertainties associated with the model parameters. The paper also examines several reliability estimate measures that would be of use for the purpose of recertification and for qualifying flight worthiness of these vessels. Specifically, deterministic values for a point estimate, mean estimate and 90/95 percent confidence estimates of the reliability are all examined for a typical flight quality vessel under constant stress. The mean and the 90/95 percent confidence estimates are computed using Monte-Carlo simulation techniques by assuming distribution statistics of model parameters based also on simulation and on the available data, especially the sample sizes represented in the data. The data for the stress rupture model are obtained from the Lawrence Livermore National Laboratories (LLNL) stress rupture testing program, carried out for the past 35 years. Deterministic as well as probabilistic sensitivities are examined.

System statistical reliability model and analysis

NASA Technical Reports Server (NTRS)

Lekach, V. S.; Rood, H.

1973-01-01

A digital computer code was developed to simulate the time-dependent behavior of the 5-kwe reactor thermoelectric system. The code was used to determine lifetime sensitivity coefficients for a number of system design parameters, such as thermoelectric module efficiency and degradation rate, radiator absorptivity and emissivity, fuel element barrier defect constant, beginning-of-life reactivity, etc. A probability distribution (mean and standard deviation) was estimated for each of these design parameters. Then, error analysis was used to obtain a probability distribution for the system lifetime (mean = 7.7 years, standard deviation = 1.1 years). From this, the probability that the system will achieve the design goal of 5 years lifetime is 0.993. This value represents an estimate of the degradation reliability of the system.

Reliability model of disk arrays RAID-5 with data striping

NASA Astrophysics Data System (ADS)

Rahman, P. A.; D'K Novikova Freyre Shavier, G.

2018-03-01

Within the scope of the this scientific paper, the simplified reliability model of disk arrays RAID-5 (redundant arrays of inexpensive disks) and an advanced reliability model offered by the authors taking into the consideration nonzero time of the faulty disk replacement and different failure rates of disks in normal state of the disk array and in degraded and rebuild states are discussed. The formula obtained by the authors for calculation of the mean time to data loss (MTTDL) of the RAID-5 disk arrays on basis of the advanced model is also presented. Finally, the technique of estimation of the initial reliability parameters, which are used in the reliability model, and the calculation examples of the mean time to data loss of the RAID-5 disk arrays for the different number of disks are also given.

An assessment of the reliability of quantitative genetics estimates in study systems with high rate of extra-pair reproduction and low recruitment.

PubMed

Bourret, A; Garant, D

2017-03-01

Quantitative genetics approaches, and particularly animal models, are widely used to assess the genetic (co)variance of key fitness related traits and infer adaptive potential of wild populations. Despite the importance of precision and accuracy of genetic variance estimates and their potential sensitivity to various ecological and population specific factors, their reliability is rarely tested explicitly. Here, we used simulations and empirical data collected from an 11-year study on tree swallow (Tachycineta bicolor), a species showing a high rate of extra-pair paternity and a low recruitment rate, to assess the importance of identity errors, structure and size of the pedigree on quantitative genetic estimates in our dataset. Our simulations revealed an important lack of precision in heritability and genetic-correlation estimates for most traits, a low power to detect significant effects and important identifiability problems. We also observed a large bias in heritability estimates when using the social pedigree instead of the genetic one (deflated heritabilities) or when not accounting for an important cause of resemblance among individuals (for example, permanent environment or brood effect) in model parameterizations for some traits (inflated heritabilities). We discuss the causes underlying the low reliability observed here and why they are also likely to occur in other study systems. Altogether, our results re-emphasize the difficulties of generalizing quantitative genetic estimates reliably from one study system to another and the importance of reporting simulation analyses to evaluate these important issues.

Batch Effect Confounding Leads to Strong Bias in Performance Estimates Obtained by Cross-Validation

PubMed Central

Delorenzi, Mauro

2014-01-01

Background With the large amount of biological data that is currently publicly available, many investigators combine multiple data sets to increase the sample size and potentially also the power of their analyses. However, technical differences (“batch effects”) as well as differences in sample composition between the data sets may significantly affect the ability to draw generalizable conclusions from such studies. Focus The current study focuses on the construction of classifiers, and the use of cross-validation to estimate their performance. In particular, we investigate the impact of batch effects and differences in sample composition between batches on the accuracy of the classification performance estimate obtained via cross-validation. The focus on estimation bias is a main difference compared to previous studies, which have mostly focused on the predictive performance and how it relates to the presence of batch effects. Data We work on simulated data sets. To have realistic intensity distributions, we use real gene expression data as the basis for our simulation. Random samples from this expression matrix are selected and assigned to group 1 (e.g., ‘control’) or group 2 (e.g., ‘treated’). We introduce batch effects and select some features to be differentially expressed between the two groups. We consider several scenarios for our study, most importantly different levels of confounding between groups and batch effects. Methods We focus on well-known classifiers: logistic regression, Support Vector Machines (SVM), k-nearest neighbors (kNN) and Random Forests (RF). Feature selection is performed with the Wilcoxon test or the lasso. Parameter tuning and feature selection, as well as the estimation of the prediction performance of each classifier, is performed within a nested cross-validation scheme. The estimated classification performance is then compared to what is obtained when applying the classifier to independent data. PMID:24967636

Validation and reliability of the sex estimation of the human os coxae using freely available DSP2 software for bioarchaeology and forensic anthropology.

PubMed

Brůžek, Jaroslav; Santos, Frédéric; Dutailly, Bruno; Murail, Pascal; Cunha, Eugenia

2017-10-01

A new tool for skeletal sex estimation based on measurements of the human os coxae is presented using skeletons from a metapopulation of identified adult individuals from twelve independent population samples. For reliable sex estimation, a posterior probability greater than 0.95 was considered to be the classification threshold: below this value, estimates are considered indeterminate. By providing free software, we aim to develop an even more disseminated method for sex estimation. Ten metric variables collected from 2,040 ossa coxa of adult subjects of known sex were recorded between 1986 and 2002 (reference sample). To test both the validity and reliability, a target sample consisting of two series of adult ossa coxa of known sex (n = 623) was used. The DSP2 software (Diagnose Sexuelle Probabiliste v2) is based on Linear Discriminant Analysis, and the posterior probabilities are calculated using an R script. For the reference sample, any combination of four dimensions provides a correct sex estimate in at least 99% of cases. The percentage of individuals for whom sex can be estimated depends on the number of dimensions; for all ten variables it is higher than 90%. Those results are confirmed in the target sample. Our posterior probability threshold of 0.95 for sex estimate corresponds to the traditional sectioning point used in osteological studies. DSP2 software is replacing the former version that should not be used anymore. DSP2 is a robust and reliable technique for sexing adult os coxae, and is also user friendly. © 2017 Wiley Periodicals, Inc.

Multi-Disciplinary System Reliability Analysis

NASA Technical Reports Server (NTRS)

Mahadevan, Sankaran; Han, Song

1997-01-01

The objective of this study is to develop a new methodology for estimating the reliability of engineering systems that encompass multiple disciplines. The methodology is formulated in the context of the NESSUS probabilistic structural analysis code developed under the leadership of NASA Lewis Research Center. The NESSUS code has been successfully applied to the reliability estimation of a variety of structural engineering systems. This study examines whether the features of NESSUS could be used to investigate the reliability of systems in other disciplines such as heat transfer, fluid mechanics, electrical circuits etc., without considerable programming effort specific to each discipline. In this study, the mechanical equivalence between system behavior models in different disciplines are investigated to achieve this objective. A new methodology is presented for the analysis of heat transfer, fluid flow, and electrical circuit problems using the structural analysis routines within NESSUS, by utilizing the equivalence between the computational quantities in different disciplines. This technique is integrated with the fast probability integration and system reliability techniques within the NESSUS code, to successfully compute the system reliability of multi-disciplinary systems. Traditional as well as progressive failure analysis methods for system reliability estimation are demonstrated, through a numerical example of a heat exchanger system involving failure modes in structural, heat transfer and fluid flow disciplines.

Reliability Problems of the Datum: Solutions for Questionnaire Responses.

ERIC Educational Resources Information Center

Bastick, Tony

Questionnaires often ask for estimates, and these estimates are given with different reliabilities. It is difficult to know the different reliabilities of single estimates and to take these into account in subsequent analyses. This paper contains a practical example to show that not taking the reliability of different responses into account can…

An Improved Internal Consistency Reliability Estimate.

ERIC Educational Resources Information Center

Cliff, Norman

1984-01-01

The proposed coefficient is derived by assuming that the average Goodman-Kruskal gamma between items of identical difficulty would be the same for items of different difficulty. An estimate of covariance between items of identical difficulty leads to an estimate of the correlation between two tests with identical distributions of difficulty.…

Reliabilities of Intraindividual Variability Indicators with Autocorrelated Longitudinal Data: Implications for Longitudinal Study Designs.

PubMed

Du, Han; Wang, Lijuan

2018-04-23

Intraindividual variability can be measured by the intraindividual standard deviation ([Formula: see text]), intraindividual variance ([Formula: see text]), estimated hth-order autocorrelation coefficient ([Formula: see text]), and mean square successive difference ([Formula: see text]). Unresolved issues exist in the research on reliabilities of intraindividual variability indicators: (1) previous research only studied conditions with 0 autocorrelations in the longitudinal responses; (2) the reliabilities of [Formula: see text] and [Formula: see text] have not been studied. The current study investigates reliabilities of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and the intraindividual mean, with autocorrelated longitudinal data. Reliability estimates of the indicators were obtained through Monte Carlo simulations. The impact of influential factors on reliabilities of the intraindividual variability indicators is summarized, and the reliabilities are compared across the indicators. Generally, all the studied indicators of intraindividual variability were more reliable with a more reliable measurement scale and more assessments. The reliabilities of [Formula: see text] were generally lower than those of [Formula: see text] and [Formula: see text], the reliabilities of [Formula: see text] were usually between those of [Formula: see text] and [Formula: see text] unless the scale reliability was large and/or the interindividual standard deviation in autocorrelation coefficients was large, and the reliabilities of the intraindividual mean were generally the highest. An R function is provided for planning longitudinal studies to ensure sufficient reliabilities of the intraindividual indicators are achieved.

The reliability of the Australasian Triage Scale: a meta-analysis

PubMed Central

Ebrahimi, Mohsen; Heydari, Abbas; Mazlom, Reza; Mirhaghi, Amir

2015-01-01

BACKGROUND: Although the Australasian Triage Scale (ATS) has been developed two decades ago, its reliability has not been defined; therefore, we present a meta-analyis of the reliability of the ATS in order to reveal to what extent the ATS is reliable. DATA SOURCES: Electronic databases were searched to March 2014. The included studies were those that reported samples size, reliability coefficients, and adequate description of the ATS reliability assessment. The guidelines for reporting reliability and agreement studies (GRRAS) were used. Two reviewers independently examined abstracts and extracted data. The effect size was obtained by the z-transformation of reliability coefficients. Data were pooled with random-effects models, and meta-regression was done based on the method of moment’s estimator. RESULTS: Six studies were included in this study at last. Pooled coefficient for the ATS was substantial 0.428 (95%CI 0.340–0.509). The rate of mis-triage was less than fifty percent. The agreement upon the adult version is higher than the pediatric version. CONCLUSION: The ATS has shown an acceptable level of overall reliability in the emergency department, but it needs more development to reach an almost perfect agreement. PMID:26056538

Validity and reliability of the minimum basic data set in estimating nosocomial acute gastroenteritis caused by rotavirus.

PubMed

Redondo-González, Olga

2015-03-01

Rotavirus is the principal cause of nosocomial acute gastroenteritis (NAGE) under 5 years of age. The objectiveis to evaluate the validity and reliability of the minimum basic dataset (MBDS) in estimating the NAGE caused by rotavirus (NAGER) and to analyze any changes during the three years that the Rotarix® and Rotateq® vaccines were used in Spain. A descriptive, retrospectivestudy was carried out in the University Hospital of Guadalajara(UHG) (Spain) between 2003-2009 using the MBDS, positive microbiological results for rotavirus (PMRs), and medical histories.Three methods of estimation were used: 1) An ICD-9-CM code 008.61 in the secondary diagnosis fields (DIAG2) of MBDS; 2) method 1 and/or PMRs with a current or recent hospitalization; and 3) the reference method or method 2 contrasted with patient medical histories. The validity of methods 1 and 2 was determined -sensitivity, specificity, predictive values and likelihood ratios (LRs)-, along with their agreement with method 3 (Kappa coefficient). In addition, the incidence rate ratio between the NAGER rate in 2007-2009 (commercialization period of both vaccines) was calculated with respect to 2003-2005 (precommercialization period). Method 1 identified 65 records with a DIAG2 of 008.61. Method 2 found 62 probable cases, and the reference method, 49 true cases. The sensitivity of the MBDS was 67 %,the positive predictive value was 51 %, and both negative LR (LR-) and reliability were moderate (LR- 0.33, Kappa coefficient 0.58). During 2007-2009, the NARGE decreased by 5 cases per 103 hospitalizations and by 9 per 104 days of hospitalization. Method 2 overestimated both the decline in incidence by 2 per 103 hospitalizations and the decreased risk per day of stay by 10 %. The MBDS found no differences between the two three-year periods, but, like method 2, showed an excellent level of diagnostic evidence (LR+ 67). The MBDS taken together with microbiological results, is more exact, safer and more reliable than

Reliability and relative validity of fish consumption data obtained in an exposure assessment study among Montreal-area sportfishers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shatenstein, B.; Kosatsky, T.; Nadon, S.

1999-02-01

A two-season exercise was undertaken in 29 high-level sportfish consumers to evaluate the reliability and accuracy of study instruments. Fishers were invited to participate after completing the main study interview (Time 1) in fall 1995 or winter 1996. Over a 4-week period, they provided a nonconsecutive 7-day weighed food record, kept a fish consumption calendar, and responded to a shortened version of the Time 1 instrument at the end of this period (Time 2). A second blood sample (at Time 2) was analyzed for whole blood mercury (Hg) and the omega-3 fatty acids eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA)more » in plasma and erythrocytes. Identical questions were compared in the Time 1 and Time 2 instruments. Reported sportfish consumption assessed by the different instruments was subjected to nutrient analysis. Three estimates of exposure to the target substances were derived from the dietary intake estimates and correlated with their respective Time 2 plasma (EPA, DHA) or blood (Hg) values, and with a kinetically derived interval-specific plasma/blood uptake value. Remarkable similarities were observed for the data derived from like questions in the Time 1 and 2 questionnaires in both seasons. However, frank discrepancies between some portion size estimates and measured values may signal cause for concern.« less

Urban air quality estimation study, phase 1

NASA Technical Reports Server (NTRS)

Diamante, J. M.; Englar, T. S., Jr.; Jazwinski, A. H.

1976-01-01

Possibilities are explored for applying estimation theory to the analysis, interpretation, and use of air quality measurements in conjunction with simulation models to provide a cost effective method of obtaining reliable air quality estimates for wide urban areas. The physical phenomenology of real atmospheric plumes from elevated localized sources is discussed. A fluctuating plume dispersion model is derived. Individual plume parameter formulations are developed along with associated a priori information. Individual measurement models are developed.

Performance of intraclass correlation coefficient (ICC) as a reliability index under various distributions in scale reliability studies.

PubMed

Mehta, Shraddha; Bastero-Caballero, Rowena F; Sun, Yijun; Zhu, Ray; Murphy, Diane K; Hardas, Bhushan; Koch, Gary

2018-04-29

Many published scale validation studies determine inter-rater reliability using the intra-class correlation coefficient (ICC). However, the use of this statistic must consider its advantages, limitations, and applicability. This paper evaluates how interaction of subject distribution, sample size, and levels of rater disagreement affects ICC and provides an approach for obtaining relevant ICC estimates under suboptimal conditions. Simulation results suggest that for a fixed number of subjects, ICC from the convex distribution is smaller than ICC for the uniform distribution, which in turn is smaller than ICC for the concave distribution. The variance component estimates also show that the dissimilarity of ICC among distributions is attributed to the study design (ie, distribution of subjects) component of subject variability and not the scale quality component of rater error variability. The dependency of ICC on the distribution of subjects makes it difficult to compare results across reliability studies. Hence, it is proposed that reliability studies should be designed using a uniform distribution of subjects because of the standardization it provides for representing objective disagreement. In the absence of uniform distribution, a sampling method is proposed to reduce the non-uniformity. In addition, as expected, high levels of disagreement result in low ICC, and when the type of distribution is fixed, any increase in the number of subjects beyond a moderately large specification such as n = 80 does not have a major impact on ICC. Copyright © 2018 John Wiley & Sons, Ltd.

Parallelized reliability estimation of reconfigurable computer networks

NASA Technical Reports Server (NTRS)

Nicol, David M.; Das, Subhendu; Palumbo, Dan

1990-01-01

A parallelized system, ASSURE, for computing the reliability of embedded avionics flight control systems which are able to reconfigure themselves in the event of failure is described. ASSURE accepts a grammar that describes a reliability semi-Markov state-space. From this it creates a parallel program that simultaneously generates and analyzes the state-space, placing upper and lower bounds on the probability of system failure. ASSURE is implemented on a 32-node Intel iPSC/860, and has achieved high processor efficiencies on real problems. Through a combination of improved algorithms, exploitation of parallelism, and use of an advanced microprocessor architecture, ASSURE has reduced the execution time on substantial problems by a factor of one thousand over previous workstation implementations. Furthermore, ASSURE's parallel execution rate on the iPSC/860 is an order of magnitude faster than its serial execution rate on a Cray-2 supercomputer. While dynamic load balancing is necessary for ASSURE's good performance, it is needed only infrequently; the particular method of load balancing used does not substantially affect performance.

Estimating child mortality and modelling its age pattern for India.

PubMed

Roy, S G

1989-06-01

"Using data [for India] on proportions of children dead...estimates of infant and child mortality are...obtained by Sullivan and Trussell modifications of [the] Brass basic method. The estimate of child survivorship function derived after logit smoothing appears to be more reliable than that obtained by the Census Actuary. The age pattern of childhood mortality is suitably modelled by [a] Weibull function defining the probability of surviving from birth to a specified age and involving two parameters of level and shape. A recently developed linearization procedure based on [a] graphical approach is adopted for estimating the parameters of the function." excerpt

Ballpark Reliability Estimation Techniques

DTIC Science & Technology

1984-04-01

containing 1955 integrated cir- cuits, yielded average values of "A" and "B" of Aav a.047 and Bay -0024 Using "av and Bav as estimates of A and B in the...wave to board (csw); hand solder ( hsc ); crimp (cmp); and weld (wld). The basic failure rate model for connections is: xp b (11E xfT x fQ) 14 where...connectors in general (Ref. Table 5.1.14-1 of MIL-HDBK-217D), the "W" value of the other types of connections (i.e., hsc , csr, and ww-) differ by orders of

Using operational data to estimate the reliable yields of water-supply wells

NASA Astrophysics Data System (ADS)

Misstear, Bruce D. R.; Beeson, Sarah

The reliable yield of a water-supply well depends on many different factors, including the properties of the well and the aquifer; the capacities of the pumps, raw-water mains, and treatment works; the interference effects from other wells; and the constraints imposed by ion licences, water quality, and environmental issues. A relatively simple methodology for estimating reliable yields has been developed that takes into account all of these factors. The methodology is based mainly on an analysis of water-level and source-output data, where such data are available. Good operational data are especially important when dealing with wells in shallow, unconfined, fissure-flow aquifers, where actual well performance may vary considerably from that predicted using a more analytical approach. Key issues in the yield-assessment process are the identification of a deepest advisable pumping water level, and the collection of the appropriate well, aquifer, and operational data. Although developed for water-supply operators in the United Kingdom, this approach to estimating the reliable yields of water-supply wells using operational data should be applicable to a wide range of hydrogeological conditions elsewhere. Résumé La productivité d'un puits capté pour l'adduction d'eau potable dépend de différents facteurs, parmi lesquels les propriétés du puits et de l'aquifère, la puissance des pompes, le traitement des eaux brutes, les effets d'interférences avec d'autres puits et les contraintes imposées par les autorisations d'exploitation, par la qualité des eaux et par les conditions environnementales. Une méthodologie relativement simple d'estimation de la productivité qui prenne en compte tous ces facteurs a été mise au point. Cette méthodologie est basée surtout sur une analyse des données concernant le niveau piézométrique et le débit de prélèvement, quand ces données sont disponibles. De bonnes données opérationnelles sont particuli

Reliability and maintainability assessment factors for reliable fault-tolerant systems

NASA Technical Reports Server (NTRS)

Bavuso, S. J.

1984-01-01

A long term goal of the NASA Langley Research Center is the development of a reliability assessment methodology of sufficient power to enable the credible comparison of the stochastic attributes of one ultrareliable system design against others. This methodology, developed over a 10 year period, is a combined analytic and simulative technique. An analytic component is the Computer Aided Reliability Estimation capability, third generation, or simply CARE III. A simulative component is the Gate Logic Software Simulator capability, or GLOSS. The numerous factors that potentially have a degrading effect on system reliability and the ways in which these factors that are peculiar to highly reliable fault tolerant systems are accounted for in credible reliability assessments. Also presented are the modeling difficulties that result from their inclusion and the ways in which CARE III and GLOSS mitigate the intractability of the heretofore unworkable mathematics.

Is One Trial Sufficient to Obtain Excellent Pressure Pain Threshold Reliability in the Low Back of Asymptomatic Individuals? A Test-Retest Study.

PubMed

Balaguier, Romain; Madeleine, Pascal; Vuillerme, Nicolas

2016-01-01

- and inter-session. Reliable measurements can be equally achieved when using the mean of two or three consecutive PPT measurements, as usually proposed in the literature, or with only the first one. Although reliability was almost perfect regardless of the conducted comparison between PPT assessments, our results suggest using two consecutive measurements to obtain higher short term absolute reliability.

Accuracy of patient-specific organ dose estimates obtained using an automated image segmentation algorithm.

PubMed

Schmidt, Taly Gilat; Wang, Adam S; Coradi, Thomas; Haas, Benjamin; Star-Lack, Josh

2016-10-01

The overall goal of this work is to develop a rapid, accurate, and automated software tool to estimate patient-specific organ doses from computed tomography (CT) scans using simulations to generate dose maps combined with automated segmentation algorithms. This work quantified the accuracy of organ dose estimates obtained by an automated segmentation algorithm. We hypothesized that the autosegmentation algorithm is sufficiently accurate to provide organ dose estimates, since small errors delineating organ boundaries will have minimal effect when computing mean organ dose. A leave-one-out validation study of the automated algorithm was performed with 20 head-neck CT scans expertly segmented into nine regions. Mean organ doses of the automatically and expertly segmented regions were computed from Monte Carlo-generated dose maps and compared. The automated segmentation algorithm estimated the mean organ dose to be within 10% of the expert segmentation for regions other than the spinal canal, with the median error for each organ region below 2%. In the spinal canal region, the median error was [Formula: see text], with a maximum absolute error of 28% for the single-atlas approach and 11% for the multiatlas approach. The results demonstrate that the automated segmentation algorithm can provide accurate organ dose estimates despite some segmentation errors.

Accuracy of patient-specific organ dose estimates obtained using an automated image segmentation algorithm

PubMed Central

Schmidt, Taly Gilat; Wang, Adam S.; Coradi, Thomas; Haas, Benjamin; Star-Lack, Josh

2016-01-01

Abstract. The overall goal of this work is to develop a rapid, accurate, and automated software tool to estimate patient-specific organ doses from computed tomography (CT) scans using simulations to generate dose maps combined with automated segmentation algorithms. This work quantified the accuracy of organ dose estimates obtained by an automated segmentation algorithm. We hypothesized that the autosegmentation algorithm is sufficiently accurate to provide organ dose estimates, since small errors delineating organ boundaries will have minimal effect when computing mean organ dose. A leave-one-out validation study of the automated algorithm was performed with 20 head-neck CT scans expertly segmented into nine regions. Mean organ doses of the automatically and expertly segmented regions were computed from Monte Carlo-generated dose maps and compared. The automated segmentation algorithm estimated the mean organ dose to be within 10% of the expert segmentation for regions other than the spinal canal, with the median error for each organ region below 2%. In the spinal canal region, the median error was −7%, with a maximum absolute error of 28% for the single-atlas approach and 11% for the multiatlas approach. The results demonstrate that the automated segmentation algorithm can provide accurate organ dose estimates despite some segmentation errors. PMID:27921070

Validity and Reliability of the Brazilian Version of the Rapid Estimate of Adult Literacy in Dentistry--BREALD-30.

PubMed

Junkes, Monica C; Fraiz, Fabian C; Sardenberg, Fernanda; Lee, Jessica Y; Paiva, Saul M; Ferreira, Fernanda M

2015-01-01

The aim of the present study was to translate, perform the cross-cultural adaptation of the Rapid Estimate of Adult Literacy in Dentistry to Brazilian-Portuguese language and test the reliability and validity of this version. After translation and cross-cultural adaptation, interviews were conducted with 258 parents/caregivers of children in treatment at the pediatric dentistry clinics and health units in Curitiba, Brazil. To test the instrument's validity, the scores of Brazilian Rapid Estimate of Adult Literacy in Dentistry (BREALD-30) were compared based on occupation, monthly household income, educational attainment, general literacy, use of dental services and three dental outcomes. The BREALD-30 demonstrated good internal reliability. Cronbach's alpha ranged from 0.88 to 0.89 when words were deleted individually. The analysis of test-retest reliability revealed excellent reproducibility (intraclass correlation coefficient = 0.983 and Kappa coefficient ranging from moderate to nearly perfect). In the bivariate analysis, BREALD-30 scores were significantly correlated with the level of general literacy (rs = 0.593) and income (rs = 0.327) and significantly associated with occupation, educational attainment, use of dental services, self-rated oral health and the respondent's perception regarding his/her child's oral health. However, only the association between the BREALD-30 score and the respondent's perception regarding his/her child's oral health remained significant in the multivariate analysis. The BREALD-30 demonstrated satisfactory psychometric properties and is therefore applicable to adults in Brazil.

Are Validity and Reliability "Relevant" in Qualitative Evaluation Research?

ERIC Educational Resources Information Center

Goodwin, Laura D.; Goodwin, William L.

1984-01-01

The views of prominant qualitative methodologists on the appropriateness of validity and reliability estimation for the measurement strategies employed in qualitative evaluations are summarized. A case is made for the relevance of validity and reliability estimation. Definitions of validity and reliability for qualitative measurement are presented…

Proposed Reliability/Cost Model

NASA Technical Reports Server (NTRS)

Delionback, L. M.

1982-01-01

New technique estimates cost of improvement in reliability for complex system. Model format/approach is dependent upon use of subsystem cost-estimating relationships (CER's) in devising cost-effective policy. Proposed methodology should have application in broad range of engineering management decisions.

A Flexible Latent Class Approach to Estimating Test-Score Reliability

ERIC Educational Resources Information Center

van der Palm, Daniël W.; van der Ark, L. Andries; Sijtsma, Klaas

2014-01-01

The latent class reliability coefficient (LCRC) is improved by using the divisive latent class model instead of the unrestricted latent class model. This results in the divisive latent class reliability coefficient (DLCRC), which unlike LCRC avoids making subjective decisions about the best solution and thus avoids judgment error. A computational…

Software For Computing Reliability Of Other Software

NASA Technical Reports Server (NTRS)

Nikora, Allen; Antczak, Thomas M.; Lyu, Michael

1995-01-01

Computer Aided Software Reliability Estimation (CASRE) computer program developed for use in measuring reliability of other software. Easier for non-specialists in reliability to use than many other currently available programs developed for same purpose. CASRE incorporates mathematical modeling capabilities of public-domain Statistical Modeling and Estimation of Reliability Functions for Software (SMERFS) computer program and runs in Windows software environment. Provides menu-driven command interface; enabling and disabling of menu options guides user through (1) selection of set of failure data, (2) execution of mathematical model, and (3) analysis of results from model. Written in C language.

Reliability Measurement for Mixed Mode Failures of 33/11 Kilovolt Electric Power Distribution Stations

PubMed Central

Alwan, Faris M.; Baharum, Adam; Hassan, Geehan S.

2013-01-01

The reliability of the electrical distribution system is a contemporary research field due to diverse applications of electricity in everyday life and diverse industries. However a few research papers exist in literature. This paper proposes a methodology for assessing the reliability of 33/11 Kilovolt high-power stations based on average time between failures. The objective of this paper is to find the optimal fit for the failure data via time between failures. We determine the parameter estimation for all components of the station. We also estimate the reliability value of each component and the reliability value of the system as a whole. The best fitting distribution for the time between failures is a three parameter Dagum distribution with a scale parameter and shape parameters and . Our analysis reveals that the reliability value decreased by 38.2% in each 30 days. We believe that the current paper is the first to address this issue and its analysis. Thus, the results obtained in this research reflect its originality. We also suggest the practicality of using these results for power systems for both the maintenance of power systems models and preventive maintenance models. PMID:23936346

Assessing the Reliability of Regional Depth-Duration-Frequency Equations for Gauged and Ungauged Sites

NASA Astrophysics Data System (ADS)

Castellarin, A.; Montanari, A.; Brath, A.

2002-12-01

The study derives Regional Depth-Duration-Frequency (RDDF) equations for a wide region of northern-central Italy (37,200 km 2) by following an adaptation of the approach originally proposed by Alila [WRR, 36(7), 2000]. The proposed RDDF equations have a rather simple structure and allow an estimation of the design storm, defined as the rainfall depth expected for a given storm duration and recurrence interval, in any location of the study area for storm durations from 1 to 24 hours and for recurrence intervals up to 100 years. The reliability of the proposed RDDF equations represents the main concern of the study and it is assessed at two different levels. The first level considers the gauged sites and compares estimates of the design storm obtained with the RDDF equations with at-site estimates based upon the observed annual maximum series of rainfall depth and with design storm estimates resulting from a regional estimator recently developed for the study area through a Hierarchical Regional Approach (HRA) [Gabriele and Arnell, WRR, 27(6), 1991]. The second level performs a reliability assessment of the RDDF equations for ungauged sites by means of a jack-knife procedure. Using the HRA estimator as a reference term, the jack-knife procedure assesses the reliability of design storm estimates provided by the RDDF equations for a given location when dealing with the complete absence of pluviometric information. The results of the analysis show that the proposed RDDF equations represent practical and effective computational means for producing a first guess of the design storm at the available raingauges and reliable design storm estimates for ungauged locations. The first author gratefully acknowledges D.H. Burn for sponsoring the submission of the present abstract.

Person Reliability

ERIC Educational Resources Information Center

Lumsden, James

1977-01-01

Person changes can be of three kinds: developmental trends, swells, and tremors. Person unreliability in the tremor sense (momentary fluctuations) can be estimated from person characteristic curves. Average person reliability for groups can be compared from item characteristic curves. (Author)

Accurate, robust and reliable calculations of Poisson-Boltzmann binding energies

PubMed Central

Nguyen, Duc D.; Wang, Bao

2017-01-01

Poisson-Boltzmann (PB) model is one of the most popular implicit solvent models in biophysical modeling and computation. The ability of providing accurate and reliable PB estimation of electrostatic solvation free energy, ΔGel, and binding free energy, ΔΔGel, is important to computational biophysics and biochemistry. In this work, we investigate the grid dependence of our PB solver (MIBPB) with SESs for estimating both electrostatic solvation free energies and electrostatic binding free energies. It is found that the relative absolute error of ΔGel obtained at the grid spacing of 1.0 Å compared to ΔGel at 0.2 Å averaged over 153 molecules is less than 0.2%. Our results indicate that the use of grid spacing 0.6 Å ensures accuracy and reliability in ΔΔGel calculation. In fact, the grid spacing of 1.1 Å appears to deliver adequate accuracy for high throughput screening. PMID:28211071

Precise attitude rate estimation using star images obtained by mission telescope for satellite missions

NASA Astrophysics Data System (ADS)

Inamori, Takaya; Hosonuma, Takayuki; Ikari, Satoshi; Saisutjarit, Phongsatorn; Sako, Nobutada; Nakasuka, Shinichi

2015-02-01

Recently, small satellites have been employed in various satellite missions such as astronomical observation and remote sensing. During these missions, the attitudes of small satellites should be stabilized to a higher accuracy to obtain accurate science data and images. To achieve precise attitude stabilization, these small satellites should estimate their attitude rate under the strict constraints of mass, space, and cost. This research presents a new method for small satellites to precisely estimate angular rate using star blurred images by employing a mission telescope to achieve precise attitude stabilization. In this method, the angular velocity is estimated by assessing the quality of a star image, based on how blurred it appears to be. Because the proposed method utilizes existing mission devices, a satellite does not require additional precise rate sensors, which makes it easier to achieve precise stabilization given the strict constraints possessed by small satellites. The research studied the relationship between estimation accuracy and parameters used to achieve an attitude rate estimation, which has a precision greater than 1 × 10-6 rad/s. The method can be applied to all attitude sensors, which use optics systems such as sun sensors and star trackers (STTs). Finally, the method is applied to the nano astrometry satellite Nano-JASMINE, and we investigate the problems that are expected to arise with real small satellites by performing numerical simulations.

Effect of windowing on lithosphere elastic thickness estimates obtained via the coherence method: Results from northern South America

NASA Astrophysics Data System (ADS)

Ojeda, GermáN. Y.; Whitman, Dean

2002-11-01

The effective elastic thickness (Te) of the lithosphere is a parameter that describes the flexural strength of a plate. A method routinely used to quantify this parameter is to calculate the coherence between the two-dimensional gravity and topography spectra. Prior to spectra calculation, data grids must be "windowed" in order to avoid edge effects. We investigated the sensitivity of Te estimates obtained via the coherence method to mirroring, Hanning and multitaper windowing techniques on synthetic data as well as on data from northern South America. These analyses suggest that the choice of windowing technique plays an important role in Te estimates and may result in discrepancies of several kilometers depending on the selected windowing method. Te results from mirrored grids tend to be greater than those from Hanning smoothed or multitapered grids. Results obtained from mirrored grids are likely to be over-estimates. This effect may be due to artificial long wavelengths introduced into the data at the time of mirroring. Coherence estimates obtained from three subareas in northern South America indicate that the average effective elastic thickness is in the range of 29-30 km, according to Hanning and multitaper windowed data. Lateral variations across the study area could not be unequivocally determined from this study. We suggest that the resolution of the coherence method does not permit evaluation of small (i.e., ˜5 km), local Te variations. However, the efficiency and robustness of the coherence method in rendering continent-scale estimates of elastic thickness has been confirmed.

Rollover risk prediction of heavy vehicles by reliability index and empirical modelling

NASA Astrophysics Data System (ADS)

Sellami, Yamine; Imine, Hocine; Boubezoul, Abderrahmane; Cadiou, Jean-Charles

2018-03-01

This paper focuses on a combination of a reliability-based approach and an empirical modelling approach for rollover risk assessment of heavy vehicles. A reliability-based warning system is developed to alert the driver to a potential rollover before entering into a bend. The idea behind the proposed methodology is to estimate the rollover risk by the probability that the vehicle load transfer ratio (LTR) exceeds a critical threshold. Accordingly, a so-called reliability index may be used as a measure to assess the vehicle safe functioning. In the reliability method, computing the maximum of LTR requires to predict the vehicle dynamics over the bend which can be in some cases an intractable problem or time-consuming. With the aim of improving the reliability computation time, an empirical model is developed to substitute the vehicle dynamics and rollover models. This is done by using the SVM (Support Vector Machines) algorithm. The preliminary obtained results demonstrate the effectiveness of the proposed approach.

Responsiveness to change and reliability of measurement of radiographic joint space width in osteoarthritis of the knee: a systematic review.

PubMed

Reichmann, W M; Maillefert, J F; Hunter, D J; Katz, J N; Conaghan, P G; Losina, E

2011-05-01

The goal of this systematic review was to report the responsiveness to change and reliability of conventional radiographic joint space width (JSW) measurement. We searched the PubMed and Embase databases using the following search criteria: [osteoarthritis (OA) (MeSH)] AND (knee) AND (X-ray OR radiography OR diagnostic imaging OR radiology OR disease progression) AND (joint space OR JSW or disease progression). We assessed responsiveness by calculating the standardized response mean (SRM). We assessed reliability using intra- and inter-reader intra-class correlation (ICC) and coefficient of variation (CV). Random-effects models were used to pool results from multiple studies. Results were stratified by study duration, design, techniques of obtaining radiographs, and measurement method. We identified 998 articles using the search terms. Of these, 32 articles (43 estimates) reported data on responsiveness of JSW measurement and 24 (50 estimates) articles reported data on measures of reliability. The overall pooled SRM was 0.33 [95% confidence interval (CI): 0.26, 0.41]. Responsiveness of change in JSW measurement was improved substantially in studies of greater than 2 years duration (0.57). Further stratifying this result in studies of greater than 2 years duration, radiographs obtained with the knee in a flexed position yielded an SRM of 0.71. Pooled intra-reader ICC was estimated at 0.97 (95% CI: 0.92, 1.00) and the intra-reader CV estimated at 3.0 (95% CI: 2.0, 4.0). Pooled inter-reader ICC was estimated at 0.93 (95% CI: 0.86, 0.99) and the inter-reader CV estimated at 3.4% (95% CI: 1.3%, 5.5%). Measurement of JSW obtained from radiographs in persons with knee is reliable. These data will be useful to clinicians who are planning RCTs where the change in minimum JSW is the outcome of interest. Copyright © 2011 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Estimation of Reliability Coefficients Using the Test Information Function and Its Modifications.

ERIC Educational Resources Information Center

Samejima, Fumiko

1994-01-01

The reliability coefficient is predicted from the test information function (TIF) or two modified TIF formulas and a specific trait distribution. Examples illustrate the variability of the reliability coefficient across different trait distributions, and results are compared with empirical reliability coefficients. (SLD)

Standard error of measurement of 5 health utility indexes across the range of health for use in estimating reliability and responsiveness.

PubMed

Palta, Mari; Chen, Han-Yang; Kaplan, Robert M; Feeny, David; Cherepanov, Dasha; Fryback, Dennis G

2011-01-01

Standard errors of measurement (SEMs) of health-related quality of life (HRQoL) indexes are not well characterized. SEM is needed to estimate responsiveness statistics, and is a component of reliability. To estimate the SEM of 5 HRQoL indexes. The National Health Measurement Study (NHMS) was a population-based survey. The Clinical Outcomes and Measurement of Health Study (COMHS) provided repeated measures. A total of 3844 randomly selected adults from the noninstitutionalized population aged 35 to 89 y in the contiguous United States and 265 cataract patients. The SF6-36v2™, QWB-SA, EQ-5D, HUI2, and HUI3 were included. An item-response theory approach captured joint variation in indexes into a composite construct of health (theta). The authors estimated 1) the test-retest standard deviation (SEM-TR) from COMHS, 2) the structural standard deviation (SEM-S) around theta from NHMS, and 3) reliability coefficients. SEM-TR was 0.068 (SF-6D), 0.087 (QWB-SA), 0.093 (EQ-5D), 0.100 (HUI2), and 0.134 (HUI3), whereas SEM-S was 0.071, 0.094, 0.084, 0.074, and 0.117, respectively. These yield reliability coefficients 0.66 (COMHS) and 0.71 (NHMS) for SF-6D, 0.59 and 0.64 for QWB-SA, 0.61 and 0.70 for EQ-5D, 0.64 and 0.80 for HUI2, and 0.75 and 0.77 for HUI3, respectively. The SEM varied across levels of health, especially for HUI2, HUI3, and EQ-5D, and was influenced by ceiling effects. Limitations. Repeated measures were 5 mo apart, and estimated theta contained measurement error. The 2 types of SEM are similar and substantial for all the indexes and vary across health.

Reliability of rehabilitative ultrasonographic imaging for muscle thickness measurement of the rhomboid major.

PubMed

Jeong, Ju Ri; Ko, Young Jun; Ha, Hyun Geun; Lee, Wan Hee

2016-03-01

This study was to establish inter-rater and intrarater reliability of the rehabilitative ultrasonographic imaging (RUSI) technique for muscle thickness measurement of the rhomboid major at rest and with the shoulder abducted to 90°. Twenty-four young adults (eight men, 16 women; right-handed; mean age [±SD], 24·4 years [±2·6]) with no history of neck, shoulder, or arm pain were recruited. Rhomboid major muscle images were obtained in the resting position and with shoulder in 90° abduction using an ultrasonography system with a 7·5-MHz linear transducer. In these two positions, the examiners found the site at which the transducer could be placed. Two examiners obtained the images of all participants in three test sessions at random. Intraclass correlation coefficients (ICC) were used to estimate reliability. All ICCs (95% CI) were >0·75, ranging from 0·93 to 0·98, which indicates good reliability. The ICCs for inter-rater reliability ranged from 0·75 to 0·94. For the absolute value of the difference in the intra-examiner reliability between the right and left ratios, the ICCs ranged from 0·58 to 0·91. In this study, the intra- and interexaminer reliability of muscle thickness measurements of the rhomboid major were good. Therefore, we suggest that muscle thickness measurements of the rhomboid major obtained with the RUSI technique would be useful for clinical rehabilitative assessment. © 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Parts and Components Reliability Assessment: A Cost Effective Approach

NASA Technical Reports Server (NTRS)

Lee, Lydia

2009-01-01

System reliability assessment is a methodology which incorporates reliability analyses performed at parts and components level such as Reliability Prediction, Failure Modes and Effects Analysis (FMEA) and Fault Tree Analysis (FTA) to assess risks, perform design tradeoffs, and therefore, to ensure effective productivity and/or mission success. The system reliability is used to optimize the product design to accommodate today?s mandated budget, manpower, and schedule constraints. Stand ard based reliability assessment is an effective approach consisting of reliability predictions together with other reliability analyses for electronic, electrical, and electro-mechanical (EEE) complex parts and components of large systems based on failure rate estimates published by the United States (U.S.) military or commercial standards and handbooks. Many of these standards are globally accepted and recognized. The reliability assessment is especially useful during the initial stages when the system design is still in the development and hard failure data is not yet available or manufacturers are not contractually obliged by their customers to publish the reliability estimates/predictions for their parts and components. This paper presents a methodology to assess system reliability using parts and components reliability estimates to ensure effective productivity and/or mission success in an efficient manner, low cost, and tight schedule.

Validity and Reliability of the Brazilian Version of the Rapid Estimate of Adult Literacy in Dentistry – BREALD-30

PubMed Central

Junkes, Monica C.; Fraiz, Fabian C.; Sardenberg, Fernanda; Lee, Jessica Y.; Paiva, Saul M.; Ferreira, Fernanda M.

2015-01-01

Objective The aim of the present study was to translate, perform the cross-cultural adaptation of the Rapid Estimate of Adult Literacy in Dentistry to Brazilian-Portuguese language and test the reliability and validity of this version. Methods After translation and cross-cultural adaptation, interviews were conducted with 258 parents/caregivers of children in treatment at the pediatric dentistry clinics and health units in Curitiba, Brazil. To test the instrument's validity, the scores of Brazilian Rapid Estimate of Adult Literacy in Dentistry (BREALD-30) were compared based on occupation, monthly household income, educational attainment, general literacy, use of dental services and three dental outcomes. Results The BREALD-30 demonstrated good internal reliability. Cronbach’s alpha ranged from 0.88 to 0.89 when words were deleted individually. The analysis of test-retest reliability revealed excellent reproducibility (intraclass correlation coefficient = 0.983 and Kappa coefficient ranging from moderate to nearly perfect). In the bivariate analysis, BREALD-30 scores were significantly correlated with the level of general literacy (rs = 0.593) and income (rs = 0.327) and significantly associated with occupation, educational attainment, use of dental services, self-rated oral health and the respondent’s perception regarding his/her child's oral health. However, only the association between the BREALD-30 score and the respondent’s perception regarding his/her child's oral health remained significant in the multivariate analysis. Conclusion The BREALD-30 demonstrated satisfactory psychometric properties and is therefore applicable to adults in Brazil. PMID:26158724

Large Sample Confidence Intervals for Item Response Theory Reliability Coefficients

ERIC Educational Resources Information Center

Andersson, Björn; Xin, Tao

2018-01-01

In applications of item response theory (IRT), an estimate of the reliability of the ability estimates or sum scores is often reported. However, analytical expressions for the standard errors of the estimators of the reliability coefficients are not available in the literature and therefore the variability associated with the estimated reliability…

1/f noise as a reliability estimation for solar panels

NASA Astrophysics Data System (ADS)

Alabedra, R.; Orsal, B.

The purpose of this work is a study of the 1/f noise from a forward biased dark solar cell as a nondestructive reliability estimation of solar panels. It is shown that one cell with a given defect can be detected in a solar panel by low frequency noise measurements at obscurity. One real solar panel of 5 cells in parallel and 5 cells in series is tested by this method. The cells for space application are n(+)p monocrystalline silicon junction with an area of 8 sq cm and a base resistivity of 10 ohm/cm. In the first part of this paper the I-V, Rd=f(1) characteristics of one cell or of a panel are not modified when a small defect is introduced by a mechanical constraint. In the second part, the theoretical results on the 1/f noise in a p-n junction under forward bias are recalled. It is shown that the noise of the cell with a defect is about 10 to 15 times higher than that of a good cell. If one good cell is replaced by a cell with defect in the panel 5 x 5, this leads to an increase of about 30 percent of the noise level of the panel.

Assuring reliability program effectiveness.

NASA Technical Reports Server (NTRS)

Ball, L. W.

1973-01-01

An attempt is made to provide simple identification and description of techniques that have proved to be most useful either in developing a new product or in improving reliability of an established product. The first reliability task is obtaining and organizing parts failure rate data. Other tasks are parts screening, tabulation of general failure rates, preventive maintenance, prediction of new product reliability, and statistical demonstration of achieved reliability. Five principal tasks for improving reliability involve the physics of failure research, derating of internal stresses, control of external stresses, functional redundancy, and failure effects control. A final task is the training and motivation of reliability specialist engineers.

Estimation of reliability of predictions and model applicability domain evaluation in the analysis of acute toxicity (LD50).

PubMed

Sazonovas, A; Japertas, P; Didziapetris, R

2010-01-01

This study presents a new type of acute toxicity (LD(50)) prediction that enables automated assessment of the reliability of predictions (which is synonymous with the assessment of the Model Applicability Domain as defined by the Organization for Economic Cooperation and Development). Analysis involved nearly 75,000 compounds from six animal systems (acute rat toxicity after oral and intraperitoneal administration; acute mouse toxicity after oral, intraperitoneal, intravenous, and subcutaneous administration). Fragmental Partial Least Squares (PLS) with 100 bootstraps yielded baseline predictions that were automatically corrected for non-linear effects in local chemical spaces--a combination called Global, Adjusted Locally According to Similarity (GALAS) modelling methodology. Each prediction obtained in this manner is provided with a reliability index value that depends on both compound's similarity to the training set (that accounts for similar trends in LD(50) variations within multiple bootstraps) and consistency of experimental results with regard to the baseline model in the local chemical environment. The actual performance of the Reliability Index (RI) was proven by its good (and uniform) correlations with Root Mean Square Error (RMSE) in all validation sets, thus providing quantitative assessment of the Model Applicability Domain. The obtained models can be used for compound screening in the early stages of drug development and prioritization for experimental in vitro testing or later in vivo animal acute toxicity studies.

Accuracy of patient specific organ-dose estimates obtained using an automated image segmentation algorithm

NASA Astrophysics Data System (ADS)

Gilat-Schmidt, Taly; Wang, Adam; Coradi, Thomas; Haas, Benjamin; Star-Lack, Josh

2016-03-01

The overall goal of this work is to develop a rapid, accurate and fully automated software tool to estimate patient-specific organ doses from computed tomography (CT) scans using a deterministic Boltzmann Transport Equation solver and automated CT segmentation algorithms. This work quantified the accuracy of organ dose estimates obtained by an automated segmentation algorithm. The investigated algorithm uses a combination of feature-based and atlas-based methods. A multiatlas approach was also investigated. We hypothesize that the auto-segmentation algorithm is sufficiently accurate to provide organ dose estimates since random errors at the organ boundaries will average out when computing the total organ dose. To test this hypothesis, twenty head-neck CT scans were expertly segmented into nine regions. A leave-one-out validation study was performed, where every case was automatically segmented with each of the remaining cases used as the expert atlas, resulting in nineteen automated segmentations for each of the twenty datasets. The segmented regions were applied to gold-standard Monte Carlo dose maps to estimate mean and peak organ doses. The results demonstrated that the fully automated segmentation algorithm estimated the mean organ dose to within 10% of the expert segmentation for regions other than the spinal canal, with median error for each organ region below 2%. In the spinal canal region, the median error was 7% across all data sets and atlases, with a maximum error of 20%. The error in peak organ dose was below 10% for all regions, with a median error below 4% for all organ regions. The multiple-case atlas reduced the variation in the dose estimates and additional improvements may be possible with more robust multi-atlas approaches. Overall, the results support potential feasibility of an automated segmentation algorithm to provide accurate organ dose estimates.

Development of a probabilistic analysis methodology for structural reliability estimation

NASA Technical Reports Server (NTRS)

Torng, T. Y.; Wu, Y.-T.

1991-01-01

The novel probabilistic analysis method for assessment of structural reliability presented, which combines fast-convolution with an efficient structural reliability analysis, can after identifying the most important point of a limit state proceed to establish a quadratic-performance function. It then transforms the quadratic function into a linear one, and applies fast convolution. The method is applicable to problems requiring computer-intensive structural analysis. Five illustrative examples of the method's application are given.

An iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions, Addendum

NASA Technical Reports Server (NTRS)

Peters, B. C., Jr.; Walker, H. F.

1975-01-01

New results and insights concerning a previously published iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions were discussed. It was shown that the procedure converges locally to the consistent maximum likelihood estimate as long as a specified parameter is bounded between two limits. Bound values were given to yield optimal local convergence.

Reliability measurement for mixed mode failures of 33/11 kilovolt electric power distribution stations.

PubMed

Alwan, Faris M; Baharum, Adam; Hassan, Geehan S

2013-01-01

The reliability of the electrical distribution system is a contemporary research field due to diverse applications of electricity in everyday life and diverse industries. However a few research papers exist in literature. This paper proposes a methodology for assessing the reliability of 33/11 Kilovolt high-power stations based on average time between failures. The objective of this paper is to find the optimal fit for the failure data via time between failures. We determine the parameter estimation for all components of the station. We also estimate the reliability value of each component and the reliability value of the system as a whole. The best fitting distribution for the time between failures is a three parameter Dagum distribution with a scale parameter [Formula: see text] and shape parameters [Formula: see text] and [Formula: see text]. Our analysis reveals that the reliability value decreased by 38.2% in each 30 days. We believe that the current paper is the first to address this issue and its analysis. Thus, the results obtained in this research reflect its originality. We also suggest the practicality of using these results for power systems for both the maintenance of power systems models and preventive maintenance models.

Challenges of Estimating the Annual Caseload of Severe Acute Malnutrition: The Case of Niger

PubMed Central

Hallarou, Mahaman; Gérard, Jean-Christophe; Donnen, Philippe; Macq, Jean

2016-01-01

Introduction Reliable prospective estimates of annual severe acute malnutrition (SAM) caseloads for treatment are needed for policy decisions and planning of quality services in the context of competing public health priorities and limited resources. This paper compares the reliability of SAM caseloads of children 6–59 months of age in Niger estimated from prevalence at the start of the year and counted from incidence at the end of the year. Methods Secondary data from two health districts for 2012 and the country overall for 2013 were used to calculate annual caseload of SAM. Prevalence and coverage were extracted from survey reports, and incidence from weekly surveillance systems. Results The prospective caseload estimate derived from prevalence and duration of illness underestimated the true burden. Similar incidence was derived from two weekly surveillance systems, but differed from that obtained from the monthly system. Incidence conversion factors were two to five times higher than recommended. Discussion Obtaining reliable prospective caseloads was challenging because prevalence is unsuitable for estimating incidence of SAM. Different SAM indicators identified different SAM populations, and duration of illness, expected contact coverage and population figures were inaccurate. The quality of primary data measurement, recording and reporting affected incidence numbers from surveillance. Coverage estimated in population surveys was rarely available, and coverage obtained by comparing admissions with prospective caseload estimates was unrealistic or impractical. Conclusions Caseload estimates derived from prevalence are unreliable and should be used with caution. Policy and service decisions that depend on these numbers may weaken performance of service delivery. Niger may improve SAM surveillance by simplifying and improving primary data collection and methods using innovative information technologies for single data entry at the first contact with the health

Reliability and validity of the Turkish version of the Rapid Estimate of Adult Literacy in Dentistry (TREALD-30).

PubMed

Peker, Kadriye; Köse, Taha Emre; Güray, Beliz; Uysal, Ömer; Erdem, Tamer Lütfi

2017-04-01

To culturally adapt the Turkish version of Rapid Estimate of Adult Literacy in Dentistry (TREALD-30) for Turkish-speaking adult dental patients and to evaluate its psychometric properties. After translation and cross-cultural adaptation, TREALD-30 was tested in a sample of 127 adult patients who attended a dental school clinic in Istanbul. Data were collected through clinical examinations and self-completed questionnaires, including TREALD-30, the Oral Health Impact Profile (OHIP), the Rapid Estimate of Adult Literacy in Medicine (REALM), two health literacy screening questions, and socio-behavioral characteristics. Psychometric properties were examined using Classical Test Theory (CTT) and Rasch analysis. Internal consistency (Cronbach's Alpha = 0.91) and test-retest reliability (Intraclass correlation coefficient = 0.99) were satisfactory for TREALD-30. It exhibited good convergent and predictive validity. Monthly family income, years of education, dental flossing, health literacy, and health literacy skills were found as stronger predictors of patients'oral health literacy (OHL). Confirmatory factor analysis (CFA) confirmed a two-factor model. The Rasch model explained 37.9% of the total variance in this dataset. In addition, TREALD-30 had eleven misfitting items, which indicated evidence of multidimensionality. The reliability indeces provided in Rasch analysis (person separation reliability = 0.91 and expected-a-posteriori/plausible reliability = 0.94) indicated that TREALD-30 had acceptable reliability. TREALD-30 showed satisfactory psychometric properties. It may be used to identify patients with low OHL. Socio-demographic factors, oral health behaviors and health literacy skills should be taken into account when planning future studies to assess the OHL in both clinical and community settings.

Development of confidence limits by pivotal functions for estimating software reliability

NASA Technical Reports Server (NTRS)

Dotson, Kelly J.

1987-01-01

The utility of pivotal functions is established for assessing software reliability. Based on the Moranda geometric de-eutrophication model of reliability growth, confidence limits for attained reliability and prediction limits for the time to the next failure are derived using a pivotal function approach. Asymptotic approximations to the confidence and prediction limits are considered and are shown to be inadequate in cases where only a few bugs are found in the software. Departures from the assumed exponentially distributed interfailure times in the model are also investigated. The effect of these departures is discussed relative to restricting the use of the Moranda model.

The Berg Balance Scale has high intra- and inter-rater reliability but absolute reliability varies across the scale: a systematic review.

PubMed

Downs, Stephen; Marquez, Jodie; Chiarelli, Pauline

2013-06-01

What is the intra-rater and inter-rater relative reliability of the Berg Balance Scale? What is the absolute reliability of the Berg Balance Scale? Does the absolute reliability of the Berg Balance Scale vary across the scale? Systematic review with meta-analysis of reliability studies. Any clinical population that has undergone assessment with the Berg Balance Scale. Relative intra-rater reliability, relative inter-rater reliability, and absolute reliability. Eleven studies involving 668 participants were included in the review. The relative intrarater reliability of the Berg Balance Scale was high, with a pooled estimate of 0.98 (95% CI 0.97 to 0.99). Relative inter-rater reliability was also high, with a pooled estimate of 0.97 (95% CI 0.96 to 0.98). A ceiling effect of the Berg Balance Scale was evident for some participants. In the analysis of absolute reliability, all of the relevant studies had an average score of 20 or above on the 0 to 56 point Berg Balance Scale. The absolute reliability across this part of the scale, as measured by the minimal detectable change with 95% confidence, varied between 2.8 points and 6.6 points. The Berg Balance Scale has a higher absolute reliability when close to 56 points due to the ceiling effect. We identified no data that estimated the absolute reliability of the Berg Balance Scale among participants with a mean score below 20 out of 56. The Berg Balance Scale has acceptable reliability, although it might not detect modest, clinically important changes in balance in individual subjects. The review was only able to comment on the absolute reliability of the Berg Balance Scale among people with moderately poor to normal balance. Copyright © 2013 Australian Physiotherapy Association. Published by .. All rights reserved.

Reliability Generalization of the Psychopathy Checklist Applied in Youthful Samples

ERIC Educational Resources Information Center

Campbell, Justin S.; Pulos, Steven; Hogan, Mike; Murry, Francie

2005-01-01

This study examines the average reliability of Hare Psychopathy Checklists (PCLs) adapted for use in samples of youthful offenders (aged 12 to 21 years). Two forms of reliability are examined: 18 alpha estimates of internal consistency and 18 intraclass correlation (two or more raters) estimates of interrater reliability. The results, an average…

Dental measurements and Bolton index reliability and accuracy obtained from 2D digital, 3D segmented CBCT, and 3d intraoral laser scanner

PubMed Central

San José, Verónica; Bellot-Arcís, Carlos; Tarazona, Beatriz; Zamora, Natalia; O Lagravère, Manuel

2017-01-01

Background To compare the reliability and accuracy of direct and indirect dental measurements derived from two types of 3D virtual models: generated by intraoral laser scanning (ILS) and segmented cone beam computed tomography (CBCT), comparing these with a 2D digital model. Material and Methods One hundred patients were selected. All patients’ records included initial plaster models, an intraoral scan and a CBCT. Patients´ dental arches were scanned with the iTero® intraoral scanner while the CBCTs were segmented to create three-dimensional models. To obtain 2D digital models, plaster models were scanned using a conventional 2D scanner. When digital models had been obtained using these three methods, direct dental measurements were measured and indirect measurements were calculated. Differences between methods were assessed by means of paired t-tests and regression models. Intra and inter-observer error were analyzed using Dahlberg´s d and coefficients of variation. Results Intraobserver and interobserver error for the ILS model was less than 0.44 mm while for segmented CBCT models, the error was less than 0.97 mm. ILS models provided statistically and clinically acceptable accuracy for all dental measurements, while CBCT models showed a tendency to underestimate measurements in the lower arch, although within the limits of clinical acceptability. Conclusions ILS and CBCT segmented models are both reliable and accurate for dental measurements. Integration of ILS with CBCT scans would get dental and skeletal information altogether. Key words:CBCT, intraoral laser scanner, 2D digital models, 3D models, dental measurements, reliability. PMID:29410764

A Survey of Software Reliability Modeling and Estimation

DTIC Science & Technology

1983-09-01

considered include: the Jelinski-Moranda Model, the ,Geometric Model,’ and Musa’s Model. A Monte -Carlo study of the behavior of the ’V"’"*least squares...ceedings Number 261, 1979, pp. 34-1, 34-11. IoelAmrit, AGieboSSukert, Alan and Goel, Ararat , "A Guidebookfor Software Reliability Assessment, 1980

Method matters: Understanding diagnostic reliability in DSM-IV and DSM-5.

PubMed

Chmielewski, Michael; Clark, Lee Anna; Bagby, R Michael; Watson, David

2015-08-01

Diagnostic reliability is essential for the science and practice of psychology, in part because reliability is necessary for validity. Recently, the DSM-5 field trials documented lower diagnostic reliability than past field trials and the general research literature, resulting in substantial criticism of the DSM-5 diagnostic criteria. Rather than indicating specific problems with DSM-5, however, the field trials may have revealed long-standing diagnostic issues that have been hidden due to a reliance on audio/video recordings for estimating reliability. We estimated the reliability of DSM-IV diagnoses using both the standard audio-recording method and the test-retest method used in the DSM-5 field trials, in which different clinicians conduct separate interviews. Psychiatric patients (N = 339) were diagnosed using the SCID-I/P; 218 were diagnosed a second time by an independent interviewer. Diagnostic reliability using the audio-recording method (N = 49) was "good" to "excellent" (M κ = .80) and comparable to the DSM-IV field trials estimates. Reliability using the test-retest method (N = 218) was "poor" to "fair" (M κ = .47) and similar to DSM-5 field-trials' estimates. Despite low test-retest diagnostic reliability, self-reported symptoms were highly stable. Moreover, there was no association between change in self-report and change in diagnostic status. These results demonstrate the influence of method on estimates of diagnostic reliability. (c) 2015 APA, all rights reserved).

The reliability of the Glasgow Coma Scale: a systematic review.

PubMed

Reith, Florence C M; Van den Brande, Ruben; Synnot, Anneliese; Gruen, Russell; Maas, Andrew I R

2016-01-01

The Glasgow Coma Scale (GCS) provides a structured method for assessment of the level of consciousness. Its derived sum score is applied in research and adopted in intensive care unit scoring systems. Controversy exists on the reliability of the GCS. The aim of this systematic review was to summarize evidence on the reliability of the GCS. A literature search was undertaken in MEDLINE, EMBASE and CINAHL. Observational studies that assessed the reliability of the GCS, expressed by a statistical measure, were included. Methodological quality was evaluated with the consensus-based standards for the selection of health measurement instruments checklist and its influence on results considered. Reliability estimates were synthesized narratively. We identified 52 relevant studies that showed significant heterogeneity in the type of reliability estimates used, patients studied, setting and characteristics of observers. Methodological quality was good (n = 7), fair (n = 18) or poor (n = 27). In good quality studies, kappa values were ≥0.6 in 85%, and all intraclass correlation coefficients indicated excellent reliability. Poor quality studies showed lower reliability estimates. Reliability for the GCS components was higher than for the sum score. Factors that may influence reliability include education and training, the level of consciousness and type of stimuli used. Only 13% of studies were of good quality and inconsistency in reported reliability estimates was found. Although the reliability was adequate in good quality studies, further improvement is desirable. From a methodological perspective, the quality of reliability studies needs to be improved. From a clinical perspective, a renewed focus on training/education and standardization of assessment is required.

Reliability of Use, Abuse, and Dependence of Four Types of Inhalants in Adolescents and Young Adults

PubMed Central

Ridenour, Ty A.; Bray, Bethany C.; Cottler, Linda B.

2007-01-01

Inhalants, as a class of drugs, consists of heterogeneous substances that include some of the most dangerous drugs on a per use basis. Research on inhalant abuse has lagged behind other drugs partly because of the need for a diagnostic instrument of different types of inhalants. This study was conducted to obtain reliability estimates for the new Substance Abuse Module DSM-IV inhalants diagnoses for four types of inhalants: aerosols, gases, nitrites, and solvents as well as different diagnostic configurations of inhalant use. Participants were 162 community sample adolescents or young adults (mean age = 20.3 years, SD = 2.4). Two-thirds of the sample was male and 83.3% was Caucasian. Kappas and intraclass correlation coefficients were computed to estimate test-retest reliabilities. Results suggested (a) abuse was more common than dependence (34.6% vs. 12.3%), (b) reliabilities of abuse criteria and diagnosis were good to excellent across subtypes, and (c) reliabilities of dependence criteria and diagnoses were poor to good across subtypes. Alternative configurations of DSM-IV criteria that were consistent with previous research on adolescents provided excellent reliabilities across subtypes of inhalants. Moreover, 11.1% of participants experienced inhalants withdrawal. PMID:17576041

Challenges in Obtaining Estimates of the Risk of Tuberculosis Infection During Overseas Deployment.

PubMed

Mancuso, James D; Geurts, Mia

2015-12-01

Estimates of the risk of tuberculosis (TB) infection resulting from overseas deployment among U.S. military service members have varied widely, and have been plagued by methodological problems. The purpose of this study was to estimate the incidence of TB infection in the U.S. military resulting from deployment. Three populations were examined: 1) a unit of 2,228 soldiers redeploying from Iraq in 2008, 2) a cohort of 1,978 soldiers followed up over 5 years after basic training at Fort Jackson in 2009, and 3) 6,062 participants in the 2011-2012 National Health and Nutrition Examination Survey (NHANES). The risk of TB infection in the deployed population was low-0.6% (95% confidence interval [CI]: 0.1-2.3%)-and was similar to the non-deployed population. The prevalence of latent TB infection (LTBI) in the U.S. population was not significantly different among deployed and non-deployed veterans and those with no military service. The limitations of these retrospective studies highlight the challenge in obtaining valid estimates of risk using retrospective data and the need for a more definitive study. Similar to civilian long-term travelers, risks for TB infection during deployment are focal in nature, and testing should be targeted to only those at increased risk. © The American Society of Tropical Medicine and Hygiene.

Reliability of air displacement plethysmography.

PubMed

Anderson, Dawn E

2007-02-01

The purpose of this study was to examine the reliability of an air displacement plethysmography device (BOD POD) over trials performed on 3 different days. Subjects consisted of 24 healthy adults (8 men, 16 women), ages 18-38 years, with body weights 46.8-93.6 kg, body mass indexes of 19.1-30.1 kg x m(-2), and percentage body fats (BF) of 7.9-43.1%. Two estimates of BF were performed on 3 days. Paired t-tests revealed no significant within-day differences in body volume (BV), thoracic gas volume (V(TG)), body density (BD), and BF. Correlations between the two V(TG) measures on a day were r = 0.86 for day 1, r = 0.93 for day 2, and r = 0.96 for day 3. BF estimates within a day had high correlations of r = 0.98. Significant differences were found between days for measures of BV, V(TG), BD, and BF. These results indicate a high reliability for within-day estimates of BF and significant differences in between-day estimates of BF using air displacement plethysmography. Reliability of BF may be increased by requiring subjects to practice the procedure for V(TG) measurement.

Measurements using orthodontic analysis software on digital models obtained by 3D scans of plaster casts : Intrarater reliability and validity.

PubMed

Czarnota, Judith; Hey, Jeremias; Fuhrmann, Robert

2016-01-01

The purpose of this work was to determine the reliability and validity of measurements performed on digital models with a desktop scanner and analysis software in comparison with measurements performed manually on conventional plaster casts. A total of 20 pairs of plaster casts reflecting the intraoral conditions of 20 fully dentate individuals were digitized using a three-dimensional scanner (D700; 3Shape). A series of defined parameters were measured both on the resultant digital models with analysis software (Ortho Analyzer; 3Shape) and on the original plaster casts with a digital caliper (Digimatic CD-15DCX; Mitutoyo). Both measurement series were repeated twice and analyzed for intrarater reliability based on intraclass correlation coefficients (ICCs). The results from the digital models were evaluated for their validity against the casts by calculating mean-value differences and associated 95 % limits of agreement (Bland-Altman method). Statistically significant differences were identified via a paired t test. Significant differences were obtained for 16 of 24 tooth-width measurements, for 2 of 5 sites of contact-point displacement in the mandibular anterior segment, for overbite, for maxillary intermolar distance, for Little's irregularity index, and for the summation indices of maxillary and mandibular incisor width. Overall, however, both the mean differences between the results obtained on the digital models versus on the plaster casts and the dispersion ranges associated with these differences suggest that the deviations incurred by the digital measuring technique are not clinically significant. Digital models are adequately reproducible and valid to be employed for routine measurements in orthodontic practice.

Examining the reliability of ADAS-Cog change scores.

PubMed

Grochowalski, Joseph H; Liu, Ying; Siedlecki, Karen L

2016-09-01

The purpose of this study was to estimate and examine ways to improve the reliability of change scores on the Alzheimer's Disease Assessment Scale, Cognitive Subtest (ADAS-Cog). The sample, provided by the Alzheimer's Disease Neuroimaging Initiative, included individuals with Alzheimer's disease (AD) (n = 153) and individuals with mild cognitive impairment (MCI) (n = 352). All participants were administered the ADAS-Cog at baseline and 1 year, and change scores were calculated as the difference in scores over the 1-year period. Three types of change score reliabilities were estimated using multivariate generalizability. Two methods to increase change score reliability were evaluated: reweighting the subtests of the scale and adding more subtests. Reliability of ADAS-Cog change scores over 1 year was low for both the AD sample (ranging from .53 to .64) and the MCI sample (.39 to .61). Reweighting the change scores from the AD sample improved reliability (.68 to .76), but lengthening provided no useful improvement for either sample. The MCI change scores had low reliability, even with reweighting and adding additional subtests. The ADAS-Cog scores had low reliability for measuring change. Researchers using the ADAS-Cog should estimate and report reliability for their use of the change scores. The ADAS-Cog change scores are not recommended for assessment of meaningful clinical change.

Reliable estimates of predictive uncertainty for an Alpine catchment using a non-parametric methodology

NASA Astrophysics Data System (ADS)

Matos, José P.; Schaefli, Bettina; Schleiss, Anton J.

2017-04-01

Uncertainty affects hydrological modelling efforts from the very measurements (or forecasts) that serve as inputs to the more or less inaccurate predictions that are produced. Uncertainty is truly inescapable in hydrology and yet, due to the theoretical and technical hurdles associated with its quantification, it is at times still neglected or estimated only qualitatively. In recent years the scientific community has made a significant effort towards quantifying this hydrologic prediction uncertainty. Despite this, most of the developed methodologies can be computationally demanding, are complex from a theoretical point of view, require substantial expertise to be employed, and are constrained by a number of assumptions about the model error distribution. These assumptions limit the reliability of many methods in case of errors that show particular cases of non-normality, heteroscedasticity, or autocorrelation. The present contribution builds on a non-parametric data-driven approach that was developed for uncertainty quantification in operational (real-time) forecasting settings. The approach is based on the concept of Pareto optimality and can be used as a standalone forecasting tool or as a postprocessor. By virtue of its non-parametric nature and a general operating principle, it can be applied directly and with ease to predictions of streamflow, water stage, or even accumulated runoff. Also, it is a methodology capable of coping with high heteroscedasticity and seasonal hydrological regimes (e.g. snowmelt and rainfall driven events in the same catchment). Finally, the training and operation of the model are very fast, making it a tool particularly adapted to operational use. To illustrate its practical use, the uncertainty quantification method is coupled with a process-based hydrological model to produce statistically reliable forecasts for an Alpine catchment located in Switzerland. Results are presented and discussed in terms of their reliability and

Reliability of reservoir firm yield determined from the historical drought of record

USGS Publications Warehouse

Archfield, S.A.; Vogel, R.M.

2005-01-01

The firm yield of a reservoir is typically defined as the maximum yield that could have been delivered without failure during the historical drought of record. In the future, reservoirs will experience droughts that are either more or less severe than the historical drought of record. The question addressed here is what the reliability of such systems will be when operated at the firm yield. To address this question, we examine the reliability of 25 hypothetical reservoirs sited across five locations in the central and western United States. These locations provided a continuous 756-month streamflow record spanning the same time interval. The firm yield of each reservoir was estimated from the historical drought of record at each location. To determine the steady-state monthly reliability of each firm-yield estimate, 12,000-month synthetic records were generated using the moving-blocks bootstrap method. Bootstrapping was repeated 100 times for each reservoir to obtain an average steady-state monthly reliability R, the number of months the reservoir did not fail divided by the total months. Values of R were greater than 0.99 for 60 percent of the study reservoirs; the other 40 percent ranged from 0.95 to 0.98. Estimates of R were highly correlated with both the level of development (ratio of firm yield to average streamflow) and average lag-1 monthly autocorrelation. Together these two predictors explained 92 percent of the variability in R, with the level of development alone explaining 85 percent of the variability. Copyright ASCE 2005.

Test Assembly Implications for Providing Reliable and Valid Subscores

ERIC Educational Resources Information Center

Lee, Minji K.; Sweeney, Kevin; Melican, Gerald J.

2017-01-01

This study investigates the relationships among factor correlations, inter-item correlations, and the reliability estimates of subscores, providing a guideline with respect to psychometric properties of useful subscores. In addition, it compares subscore estimation methods with respect to reliability and distinctness. The subscore estimation…

Reliability reporting across studies using the Buss Durkee Hostility Inventory.

PubMed

Vassar, Matt; Hale, William

2009-01-01

Empirical research on anger and hostility has pervaded the academic literature for more than 50 years. Accurate measurement of anger/hostility and subsequent interpretation of results requires that the instruments yield strong psychometric properties. For consistent measurement, reliability estimates must be calculated with each administration, because changes in sample characteristics may alter the scale's ability to generate reliable scores. Therefore, the present study was designed to address reliability reporting practices for a widely used anger assessment, the Buss Durkee Hostility Inventory (BDHI). Of the 250 published articles reviewed, 11.2% calculated and presented reliability estimates for the data at hand, 6.8% cited estimates from a previous study, and 77.1% made no mention of score reliability. Mean alpha estimates of scores for BDHI subscales generally fell below acceptable standards. Additionally, no detectable pattern was found between reporting practices and publication year or journal prestige. Areas for future research are also discussed.

Trunk-acceleration based assessment of gait parameters in older persons: a comparison of reliability and validity of four inverted pendulum based estimations.

PubMed

Zijlstra, Agnes; Zijlstra, Wiebren

2013-09-01

Inverted pendulum (IP) models of human walking allow for wearable motion-sensor based estimations of spatio-temporal gait parameters during unconstrained walking in daily-life conditions. At present it is unclear to what extent different IP based estimations yield different results, and reliability and validity have not been investigated in older persons without a specific medical condition. The aim of this study was to compare reliability and validity of four different IP based estimations of mean step length in independent-living older persons. Participants were assessed twice and walked at different speeds while wearing a tri-axial accelerometer at the lower back. For all step-length estimators, test-retest intra-class correlations approached or were above 0.90. Intra-class correlations with reference step length were above 0.92 with a mean error of 0.0 cm when (1) multiplying the estimated center-of-mass displacement during a step by an individual correction factor in a simple IP model, or (2) adding an individual constant for bipedal stance displacement to the estimated displacement during single stance in a 2-phase IP model. When applying generic corrections or constants in all subjects (i.e. multiplication by 1.25, or adding 75% of foot length), correlations were above 0.75 with a mean error of respectively 2.0 and 1.2 cm. Although the results indicate that an individual adjustment of the IP models provides better estimations of mean step length, the ease of a generic adjustment can be favored when merely evaluating intra-individual differences. Further studies should determine the validity of these IP based estimations for assessing gait in daily life. Copyright © 2013 Elsevier B.V. All rights reserved.

ASSESSING AND COMBINING RELIABILITY OF PROTEIN INTERACTION SOURCES

PubMed Central

LEACH, SONIA; GABOW, AARON; HUNTER, LAWRENCE; GOLDBERG, DEBRA S.

2008-01-01

Integrating diverse sources of interaction information to create protein networks requires strategies sensitive to differences in accuracy and coverage of each source. Previous integration approaches calculate reliabilities of protein interaction information sources based on congruity to a designated ‘gold standard.’ In this paper, we provide a comparison of the two most popular existing approaches and propose a novel alternative for assessing reliabilities which does not require a gold standard. We identify a new method for combining the resultant reliabilities and compare it against an existing method. Further, we propose an extrinsic approach to evaluation of reliability estimates, considering their influence on the downstream tasks of inferring protein function and learning regulatory networks from expression data. Results using this evaluation method show 1) our method for reliability estimation is an attractive alternative to those requiring a gold standard and 2) the new method for combining reliabilities is less sensitive to noise in reliability assignments than the similar existing technique. PMID:17990508

Standard error of measurement of five health utility indexes across the range of health for use in estimating reliability and responsiveness

PubMed Central

Palta, Mari; Chen, Han-Yang; Kaplan, Robert M.; Feeny, David; Cherepanov, Dasha; Fryback, Dennis

2011-01-01

Background Standard errors of measurement (SEMs) of health related quality of life (HRQoL) indexes are not well characterized. SEM is needed to estimate responsiveness statistics and provides guidance on using indexes on the individual and group level. SEM is also a component of reliability. Purpose To estimate SEM of five HRQoL indexes. Design The National Health Measurement Study (NHMS) was a population based telephone survey. The Clinical Outcomes and Measurement of Health Study (COMHS) provided repeated measures 1 and 6 months post cataract surgery. Subjects 3844 randomly selected adults from the non-institutionalized population 35 to 89 years old in the contiguous United States and 265 cataract patients. Measurements The SF6-36v2™, QWB-SA, EQ-5D, HUI2 and HUI3 were included. An item-response theory (IRT) approach captured joint variation in indexes into a composite construct of health (theta). We estimated: (1) the test-retest standard deviation (SEM-TR) from COMHS, (2) the structural standard deviation (SEM-S) around the composite construct from NHMS and (3) corresponding reliability coefficients. Results SEM-TR was 0.068 (SF-6D), 0.087 (QWB-SA), 0.093 (EQ-5D), 0.100 (HUI2) and 0.134 (HUI3), while SEM-S was 0.071, 0.094, 0.084, 0.074 and 0.117, respectively. These translate into reliability coefficients for SF-6D: 0.66 (COMHS) and 0.71 (NHMS), for QWB: 0.59 and 0.64, for EQ-5D: 0.61 and 0.70 for HUI2: 0.64 and 0.80, and for HUI3: 0.75 and 0.77, respectively. The SEM varied considerably across levels of health, especially for HUI2, HUI3 and EQ-5D, and was strongly influenced by ceiling effects. Limitations Repeated measures were five months apart and estimated theta contain measurement error. Conclusions The two types of SEM are similar and substantial for all the indexes, and vary across the range of health. PMID:20935280

On-orbit spacecraft reliability

NASA Technical Reports Server (NTRS)

Bloomquist, C.; Demars, D.; Graham, W.; Henmi, P.

1978-01-01

Operational and historic data for 350 spacecraft from 52 U.S. space programs were analyzed for on-orbit reliability. Failure rates estimates are made for on-orbit operation of spacecraft subsystems, components, and piece parts, as well as estimates of failure probability for the same elements during launch. Confidence intervals for both parameters are also given. The results indicate that: (1) the success of spacecraft operation is only slightly affected by most reported incidents of anomalous behavior; (2) the occurrence of the majority of anomalous incidents could have been prevented piror to launch; (3) no detrimental effect of spacecraft dormancy is evident; (4) cycled components in general are not demonstrably less reliable than uncycled components; and (5) application of product assurance elements is conductive to spacecraft success.

Reliability of the Walker Cranial Nonmetric Method and Implications for Sex Estimation.

PubMed

Lewis, Cheyenne J; Garvin, Heather M

2016-05-01

The cranial trait scoring method presented in Buikstra and Ubelaker (Standards for data collection from human skeletal remains. Fayetteville, AR: Arkansas Archeological Survey Research Series No. 44, 1994) and Walker (Am J Phys Anthropol, 136, 2008 and 39) is the most common nonmetric cranial sex estimation method utilized by physical and forensic anthropologists. As such, the reliability and accuracy of the method is vital to ensure its validity in forensic applications. In this study, inter- and intra-observer error rates for the Walker scoring method were calculated using a sample of U.S. White and Black individuals (n = 135). Cohen's weighted kappas, intraclass correlation coefficients, and percentage agreements indicate good agreement between trials and observers for all traits except the mental eminence. Slight disagreement in scoring, however, was found to impact sex classifications, leading to lower accuracy rates than those published by Walker. Furthermore, experience does appear to impact trait scoring and sex classification. The use of revised population-specific equations that avoid the mental eminence is highly recommended to minimize the potential for misclassifications. © 2016 American Academy of Forensic Sciences.

Reliability of Test Scores in Nonparametric Item Response Theory.

ERIC Educational Resources Information Center

Sijtsma, Klaas; Molenaar, Ivo W.

1987-01-01

Three methods for estimating reliability are studied within the context of nonparametric item response theory. Two were proposed originally by Mokken and a third is developed in this paper. Using a Monte Carlo strategy, these three estimation methods are compared with four "classical" lower bounds to reliability. (Author/JAZ)

Reliability and validity of a Tutorial Group Effectiveness Instrument.

PubMed

Singaram, Veena S; Van Der Vleuten, Cees P M; Van Berkel, Henk; Dolmans, Diana H J M

2010-01-01

Tutorial group effectiveness is essential for the success of learning in problem-based learning (PBL). Less effective and dysfunctional groups compromise the quality of students learning in PBL. This article aims to report on the reliability and validity of an instrument aimed at measuring tutorial group effectiveness in PBL. The items within the instrument are clustered around motivational and cognitive factors based on Slavin's theoretical framework. A confirmatory factor analysis (CFA) was carried out to estimate the validity of the instrument. Furthermore, generalizability studies were conducted and alpha coefficients were computed to determine the reliability and homogeneity of each factor. The CFA indicated that a three-factor model comprising 19 items showed a good fit with the data. Alpha coefficients per factor were high. The findings of the generalizability studies indicated that at least 9-10 student responses are needed in order to obtain reliable data at the tutorial group level. The instrument validated in this study has the potential to provide faculty and students with diagnostic information and feedback about student behaviors that enhance and hinder tutorial group effectiveness.

A Monte Carlo Simulation Investigating the Validity and Reliability of Ability Estimation in Item Response Theory with Speeded Computer Adaptive Tests

ERIC Educational Resources Information Center

Schmitt, T. A.; Sass, D. A.; Sullivan, J. R.; Walker, C. M.

2010-01-01

Imposed time limits on computer adaptive tests (CATs) can result in examinees having difficulty completing all items, thus compromising the validity and reliability of ability estimates. In this study, the effects of speededness were explored in a simulated CAT environment by varying examinee response patterns to end-of-test items. Expectedly,…

The Reliability and Validity of Using Regression Residuals to Measure Institutional Effectiveness in Promoting Degree Completion

ERIC Educational Resources Information Center

Horn, Aaron S.; Lee, Giljae

2016-01-01

A relatively simple way of measuring institutional effectiveness in relation to degree completion is to estimate the difference between an actual and predicted graduation rate, but the reliability and validity of this method have not been thoroughly examined. Longitudinal data were obtained from IPEDS for both public and private not-for-profit…

Getting It Right Matters: Climate Spectra and Their Estimation

NASA Astrophysics Data System (ADS)

Privalsky, Victor; Yushkov, Vladislav

2018-06-01

In many recent publications, climate spectra estimated with different methods from observed, GCM-simulated, and reconstructed time series contain many peaks at time scales from a few years to many decades and even centuries. However, respective spectral estimates obtained with the autoregressive (AR) and multitapering (MTM) methods showed that spectra of climate time series are smooth and contain no evidence of periodic or quasi-periodic behavior. Four order selection criteria for the autoregressive models were studied and proven sufficiently reliable for 25 time series of climate observations at individual locations or spatially averaged at local-to-global scales. As time series of climate observations are short, an alternative reliable nonparametric approach is Thomson's MTM. These results agree with both the earlier climate spectral analyses and the Markovian stochastic model of climate.

Reliability Analysis and Reliability-Based Design Optimization of Circular Composite Cylinders Under Axial Compression

NASA Technical Reports Server (NTRS)

Rais-Rohani, Masoud

2001-01-01

This report describes the preliminary results of an investigation on component reliability analysis and reliability-based design optimization of thin-walled circular composite cylinders with average diameter and average length of 15 inches. Structural reliability is based on axial buckling strength of the cylinder. Both Monte Carlo simulation and First Order Reliability Method are considered for reliability analysis with the latter incorporated into the reliability-based structural optimization problem. To improve the efficiency of reliability sensitivity analysis and design optimization solution, the buckling strength of the cylinder is estimated using a second-order response surface model. The sensitivity of the reliability index with respect to the mean and standard deviation of each random variable is calculated and compared. The reliability index is found to be extremely sensitive to the applied load and elastic modulus of the material in the fiber direction. The cylinder diameter was found to have the third highest impact on the reliability index. Also the uncertainty in the applied load, captured by examining different values for its coefficient of variation, is found to have a large influence on cylinder reliability. The optimization problem for minimum weight is solved subject to a design constraint on element reliability index. The methodology, solution procedure and optimization results are included in this report.

Reliable Quantification of the Potential for Equations Based on Spot Urine Samples to Estimate Population Salt Intake: Protocol for a Systematic Review and Meta-Analysis.

PubMed

Huang, Liping; Crino, Michelle; Wu, Jason Hy; Woodward, Mark; Land, Mary-Anne; McLean, Rachael; Webster, Jacqui; Enkhtungalag, Batsaikhan; Nowson, Caryl A; Elliott, Paul; Cogswell, Mary; Toft, Ulla; Mill, Jose G; Furlanetto, Tania W; Ilich, Jasminka Z; Hong, Yet Hoi; Cohall, Damian; Luzardo, Leonella; Noboa, Oscar; Holm, Ellen; Gerbes, Alexander L; Senousy, Bahaa; Pinar Kara, Sonat; Brewster, Lizzy M; Ueshima, Hirotsugu; Subramanian, Srinivas; Teo, Boon Wee; Allen, Norrina; Choudhury, Sohel Reza; Polonia, Jorge; Yasuda, Yoshinari; Campbell, Norm Rc; Neal, Bruce; Petersen, Kristina S

2016-09-21

Methods based on spot urine samples (a single sample at one time-point) have been identified as a possible alternative approach to 24-hour urine samples for determining mean population salt intake. The aim of this study is to identify a reliable method for estimating mean population salt intake from spot urine samples. This will be done by comparing the performance of existing equations against one other and against estimates derived from 24-hour urine samples. The effects of factors such as ethnicity, sex, age, body mass index, antihypertensive drug use, health status, and timing of spot urine collection will be explored. The capacity of spot urine samples to measure change in salt intake over time will also be determined. Finally, we aim to develop a novel equation (or equations) that performs better than existing equations to estimate mean population salt intake. A systematic review and meta-analysis of individual participant data will be conducted. A search has been conducted to identify human studies that report salt (or sodium) excretion based upon 24-hour urine samples and spot urine samples. There were no restrictions on language, study sample size, or characteristics of the study population. MEDLINE via OvidSP (1946-present), Premedline via OvidSP, EMBASE, Global Health via OvidSP (1910-present), and the Cochrane Library were searched, and two reviewers identified eligible studies. The authors of these studies will be invited to contribute data according to a standard format. Individual participant records will be compiled and a series of analyses will be completed to: (1) compare existing equations for estimating 24-hour salt intake from spot urine samples with 24-hour urine samples, and assess the degree of bias according to key demographic and clinical characteristics; (2) assess the reliability of using spot urine samples to measure population changes in salt intake overtime; and (3) develop a novel equation that performs better than existing equations

Practical Issues in Implementing Software Reliability Measurement

NASA Technical Reports Server (NTRS)

Nikora, Allen P.; Schneidewind, Norman F.; Everett, William W.; Munson, John C.; Vouk, Mladen A.; Musa, John D.

1999-01-01

Many ways of estimating software systems' reliability, or reliability-related quantities, have been developed over the past several years. Of particular interest are methods that can be used to estimate a software system's fault content prior to test, or to discriminate between components that are fault-prone and those that are not. The results of these methods can be used to: 1) More accurately focus scarce fault identification resources on those portions of a software system most in need of it. 2) Estimate and forecast the risk of exposure to residual faults in a software system during operation, and develop risk and safety criteria to guide the release of a software system to fielded use. 3) Estimate the efficiency of test suites in detecting residual faults. 4) Estimate the stability of the software maintenance process.

A Bayesian modification to the Jelinski-Moranda software reliability growth model

NASA Technical Reports Server (NTRS)

Littlewood, B.; Sofer, A.

1983-01-01

The Jelinski-Moranda (JM) model for software reliability was examined. It is suggested that a major reason for the poor results given by this model is the poor performance of the maximum likelihood method (ML) of parameter estimation. A reparameterization and Bayesian analysis, involving a slight modelling change, are proposed. It is shown that this new Bayesian-Jelinski-Moranda model (BJM) is mathematically quite tractable, and several metrics of interest to practitioners are obtained. The BJM and JM models are compared by using several sets of real software failure data collected and in all cases the BJM model gives superior reliability predictions. A change in the assumption which underlay both models to present the debugging process more accurately is discussed.

Disease severity assessment in epidemiological studies: accuracy and reliability of visual estimates of Septoria leaf blotch (SLB) in winter wheat

USDA-ARS?s Scientific Manuscript database

The accuracy and reliability of visual assessments of SLB severity by raters (i.e. one plant pathologist with extensive experience and three other raters trained prior to field observations using standard area diagrams and DISTRAIN) was determined by comparison with assumed actual values obtained by...

Scale Reliability Evaluation with Heterogeneous Populations

ERIC Educational Resources Information Center

Raykov, Tenko; Marcoulides, George A.

2015-01-01

A latent variable modeling approach for scale reliability evaluation in heterogeneous populations is discussed. The method can be used for point and interval estimation of reliability of multicomponent measuring instruments in populations representing mixtures of an unknown number of latent classes or subpopulations. The procedure is helpful also…

The Yale-Brown Obsessive Compulsive Scale: A Reliability Generalization Meta-Analysis.

PubMed

López-Pina, José Antonio; Sánchez-Meca, Julio; López-López, José Antonio; Marín-Martínez, Fulgencio; Núñez-Núñez, Rosa Maria; Rosa-Alcázar, Ana I; Gómez-Conesa, Antonia; Ferrer-Requena, Josefa

2015-10-01

The Yale-Brown Obsessive Compulsive Scale (Y-BOCS) is the most frequently applied test to assess obsessive compulsive symptoms. We conducted a reliability generalization meta-analysis on the Y-BOCS to estimate the average reliability, examine the variability among the reliability estimates, search for moderators, and propose a predictive model that researchers and clinicians can use to estimate the expected reliability of the Y-BOCS. We included studies where the Y-BOCS was applied to a sample of adults and reliability estimate was reported. Out of the 11,490 references located, 144 studies met the selection criteria. For the total scale, the mean reliability was 0.866 for coefficients alpha, 0.848 for test-retest correlations, and 0.922 for intraclass correlations. The moderator analyses led to a predictive model where the standard deviation of the total test and the target population (clinical vs. nonclinical) explained 38.6% of the total variability among coefficients alpha. Finally, clinical implications of the results are discussed. © The Author(s) 2014.

Methods and Costs to Achieve Ultra Reliable Life Support

NASA Technical Reports Server (NTRS)

Jones, Harry W.

2012-01-01

A published Mars mission is used to explore the methods and costs to achieve ultra reliable life support. The Mars mission and its recycling life support design are described. The life support systems were made triply redundant, implying that each individual system will have fairly good reliability. Ultra reliable life support is needed for Mars and other long, distant missions. Current systems apparently have insufficient reliability. The life cycle cost of the Mars life support system is estimated. Reliability can be increased by improving the intrinsic system reliability, adding spare parts, or by providing technically diverse redundant systems. The costs of these approaches are estimated. Adding spares is least costly but may be defeated by common cause failures. Using two technically diverse systems is effective but doubles the life cycle cost. Achieving ultra reliability is worth its high cost because the penalty for failure is very high.

Reliability of digital reactor protection system based on extenics.

PubMed

Zhao, Jing; He, Ya-Nan; Gu, Peng-Fei; Chen, Wei-Hua; Gao, Feng

2016-01-01

After the Fukushima nuclear accident, safety of nuclear power plants (NPPs) is widespread concerned. The reliability of reactor protection system (RPS) is directly related to the safety of NPPs, however, it is difficult to accurately evaluate the reliability of digital RPS. The method is based on estimating probability has some uncertainties, which can not reflect the reliability status of RPS dynamically and support the maintenance and troubleshooting. In this paper, the reliability quantitative analysis method based on extenics is proposed for the digital RPS (safety-critical), by which the relationship between the reliability and response time of RPS is constructed. The reliability of the RPS for CPR1000 NPP is modeled and analyzed by the proposed method as an example. The results show that the proposed method is capable to estimate the RPS reliability effectively and provide support to maintenance and troubleshooting of digital RPS system.

The Estimation of the IRT Reliability Coefficient and Its Lower and Upper Bounds, with Comparisons to CTT Reliability Statistics

ERIC Educational Resources Information Center

Kim, Seonghoon; Feldt, Leonard S.

2010-01-01

The primary purpose of this study is to investigate the mathematical characteristics of the test reliability coefficient rho[subscript XX'] as a function of item response theory (IRT) parameters and present the lower and upper bounds of the coefficient. Another purpose is to examine relative performances of the IRT reliability statistics and two…

Estimating Sleep from Multisensory Armband Measurements: Validity and Reliability in Teens

PubMed Central

Roane, Brandy M.; Van Reen, Eliza; Hart, Chantelle N.; Wing, Rena; Carskadon, Mary A.

2015-01-01

SUMMARY Given the recognition that sleep may influence obesity risk, there is increasing interest in measuring sleep parameters within obesity studies. The goal of the current analyses was to determine whether the SenseWear® Pro3 Armband (armband), typically used to assess physical activity, is reliable at assessing sleep parameters. We compared the armband to the AMI Motionlogger® (actigraph), a validated activity monitor for sleep assessment and to polysomnography (PSG), the gold standard for assessing sleep. Participants were twenty adolescents (mean age=15.5 years) with a mean BMI %tile of 63.7. All participants wore the armband and actigraph on their non-dominant arm while in-lab during a nocturnal PSG recording (600 minutes). Epoch-by-epoch sleep/wake data and concordance of sleep parameters were examined. No significant sleep parameter differences were found between the armband and PSG; the actigraph tended to overestimate sleep and underestimate wake compared to PSG. Both devices showed high sleep sensitivity, but lower wake detection rates. Bland-Altman plots showed large individual differences in armband sleep parameter concordance rates. The armband did well estimating sleep overall with group results more similar to PSG than the actigraph; however, the armband was less accurate at an individual level than the actigraph. PMID:26126746

Estimating sleep from multisensory armband measurements: validity and reliability in teens.

PubMed

Roane, Brandy M; Van Reen, Eliza; Hart, Chantelle N; Wing, Rena; Carskadon, Mary A

2015-12-01

Given the recognition that sleep may influence obesity risk, there is increasing interest in measuring sleep parameters within obesity studies. The goal of the current analyses was to determine whether the SenseWear(®) Pro3 Armband (armband), typically used to assess physical activity, is reliable at assessing sleep parameters. The armband was compared with the AMI Motionlogger(®) (actigraph), a validated activity monitor for sleep assessment, and with polysomnography, the gold standard for assessing sleep. Participants were 20 adolescents (mean age = 15.5 years) with a mean body mass index percentile of 63.7. All participants wore the armband and actigraph on their non-dominant arm while in-lab during a nocturnal polysomnographic recording (600 min). Epoch-by-epoch sleep/wake data and concordance of sleep parameters were examined. No significant sleep parameter differences were found between the armband and polysomnography; the actigraph tended to overestimate sleep and underestimate wake compared with polysomnography. Both devices showed high sleep sensitivity, but lower wake detection rates. Bland-Altman plots showed large individual differences in armband sleep parameter concordance rates. The armband did well estimating sleep overall, with group results more similar to polysomnography than the actigraph; however, the armband was less accurate at an individual level than the actigraph. © 2015 European Sleep Research Society.

An Optimal Estimation Method to Obtain Surface Layer Turbulent Fluxes from Profile Measurements

NASA Astrophysics Data System (ADS)

Kang, D.

2015-12-01

In the absence of direct turbulence measurements, the turbulence characteristics of the atmospheric surface layer are often derived from measurements of the surface layer mean properties based on Monin-Obukhov Similarity Theory (MOST). This approach requires two levels of the ensemble mean wind, temperature, and water vapor, from which the fluxes of momentum, sensible heat, and water vapor can be obtained. When only one measurement level is available, the roughness heights and the assumed properties of the corresponding variables at the respective roughness heights are used. In practice, the temporal mean with large number of samples are used in place of the ensemble mean. However, in many situations the samples of data are taken from multiple levels. It is thus desirable to derive the boundary layer flux properties using all measurements. In this study, we used an optimal estimation approach to derive surface layer properties based on all available measurements. This approach assumes that the samples are taken from a population whose ensemble mean profile follows the MOST. An optimized estimate is obtained when the results yield a minimum cost function defined as a weighted summation of all error variance at each sample altitude. The weights are based one sample data variance and the altitude of the measurements. This method was applied to measurements in the marine atmospheric surface layer from a small boat using radiosonde on a tethered balloon where temperature and relative humidity profiles in the lowest 50 m were made repeatedly in about 30 minutes. We will present the resultant fluxes and the derived MOST mean profiles using different sets of measurements. The advantage of this method over the 'traditional' methods will be illustrated. Some limitations of this optimization method will also be discussed. Its application to quantify the effects of marine surface layer environment on radar and communication signal propagation will be shown as well.

Principle of maximum entropy for reliability analysis in the design of machine components

NASA Astrophysics Data System (ADS)

Zhang, Yimin

2018-03-01

We studied the reliability of machine components with parameters that follow an arbitrary statistical distribution using the principle of maximum entropy (PME). We used PME to select the statistical distribution that best fits the available information. We also established a probability density function (PDF) and a failure probability model for the parameters of mechanical components using the concept of entropy and the PME. We obtained the first four moments of the state function for reliability analysis and design. Furthermore, we attained an estimate of the PDF with the fewest human bias factors using the PME. This function was used to calculate the reliability of the machine components, including a connecting rod, a vehicle half-shaft, a front axle, a rear axle housing, and a leaf spring, which have parameters that typically follow a non-normal distribution. Simulations were conducted for comparison. This study provides a design methodology for the reliability of mechanical components for practical engineering projects.

Estimates of the solar internal angular velocity obtained with the Mt. Wilson 60-foot solar tower

NASA Technical Reports Server (NTRS)

Rhodes, Edward J., Jr.; Cacciani, Alessandro; Woodard, Martin; Tomczyk, Steven; Korzennik, Sylvain

1987-01-01

Estimates are obtained of the solar internal angular velocity from measurements of the frequency splittings of p-mode oscillations. A 16-day time series of full-disk Dopplergrams obtained during July and August 1984 at the 60-foot tower telescope of the Mt. Wilson Observatory is analyzed. Power spectra were computed for all of the zonal, tesseral, and sectoral p-modes from l = 0 to 89 and for all of the sectoral p-modes from l = 90 to 200. A mean power spectrum was calculated for each degree up to 89. The frequency differences of all of the different nonzonal modes were calculated for these mean power spectra.

Benchmarking passive seismic methods of estimating the depth of velocity interfaces down to ~300 m

NASA Astrophysics Data System (ADS)

Czarnota, Karol; Gorbatov, Alexei

2016-04-01

In shallow passive seismology it is generally accepted that the spatial autocorrelation (SPAC) method is more robust than the horizontal-over-vertical spectral ratio (HVSR) method at resolving the depth to surface-wave velocity (Vs) interfaces. Here we present results of a field test of these two methods over ten drill sites in western Victoria, Australia. The target interface is the base of Cenozoic unconsolidated to semi-consolidated clastic and/or carbonate sediments of the Murray Basin, which overlie Paleozoic crystalline rocks. Depths of this interface intersected in drill holes are between ~27 m and ~300 m. Seismometers were deployed in a three-arm spiral array, with a radius of 250 m, consisting of 13 Trillium Compact 120 s broadband instruments. Data were acquired at each site for 7-21 hours. The Vs architecture beneath each site was determined through nonlinear inversion of HVSR and SPAC data using the neighbourhood algorithm, implemented in the geopsy modelling package (Wathelet, 2005, GRL v35). The HVSR technique yielded depth estimates of the target interface (Vs > 1000 m/s) generally within ±20% error. Successful estimates were even obtained at a site with an inverted velocity profile, where Quaternary basalts overlie Neogene sediments which in turn overlie the target basement. Half of the SPAC estimates showed significantly higher errors than were obtained using HVSR. Joint inversion provided the most reliable estimates but was unstable at three sites. We attribute the surprising success of HVSR over SPAC to a low content of transient signals within the seismic record caused by low levels of anthropogenic noise at the benchmark sites. At a few sites SPAC waveform curves showed clear overtones suggesting that more reliable SPAC estimates may be obtained utilizing a multi-modal inversion. Nevertheless, our study indicates that reliable basin thickness estimates in the Australian conditions tested can be obtained utilizing HVSR data from a single

Reliability, repeatability, and reproducibility of pulmonary transit time assessment by contrast enhanced echocardiography.

PubMed

Herold, Ingeborg H F; Saporito, Salvatore; Bouwman, R Arthur; Houthuizen, Patrick; van Assen, Hans C; Mischi, Massimo; Korsten, Hendrikus H M

2016-01-05

The aim of this study is to investigate the inter and intra-rater reliability, repeatability, and reproducibility of pulmonary transit time (PTT) measurement in patients using contrast enhanced ultrasound (CEUS), as an indirect measure of preload and left ventricular function. Mean transit times (MTT) were measured by drawing a region of interest (ROI) in right and left cardiac ventricle in the CEUS loops. Acoustic intensity dilution curves were obtained from the ROIs. MTTs were calculated by applying model-based fitting on the dilution curves. PTT was calculated as the difference of the MTTs. Eight raters with different levels of experience measured the PTT (time moment 1) and repeated the measurement within a week (time moment 2). Reliability and agreement were assessed using intra-class correlations (ICC) and Bland-Altman analysis. Repeatability was tested by estimating the variance of means (ANOVA) of three injections in each patient at different doses. Reproducibility was tested by the ICC of the two time moments. Fifteen patients with heart failure were included. The mean PTT was 11.8 ± 3.1 s at time moment 1 and 11.7 ± 2.9 s at time moment 2. The inter-rater reliability for PTT was excellent (ICC = 0.94). The intra-rater reliability per rater was between 0.81-0.99. Bland-Altman analysis revealed a bias of 0.10 s within the rater groups. Reproducibility for PTT showed an ICC = 0.94 between the two time moments. ANOVA showed no significant difference between the means of the three different doses F = 0.048 (P = 0.95). The mean and standard deviation for PTT estimates at three different doses was 11.6 ± 3.3 s. PTT estimation using CEUS shows a high inter- and intra-rater reliability, repeatability at three different doses, and reproducibility by ROI drawing. This makes the minimally invasive PTT measurement using contrast echocardiography ready for clinical evaluation in patients with heart failure and for preload estimation.

Tracking Biases: An Update to the Validity and Reliability of Alcohol Retail Sales Data for Estimating Population Consumption in Scotland.

PubMed

Henderson, Audrey; Robinson, Mark; McAdams, Rachel; McCartney, Gerry; Beeston, Clare

2016-05-01

To highlight the importance of monitoring biases when using retail sales data to estimate population alcohol consumption. Previously, we identified and where possible quantified sources of bias that may lead to under- or overestimation of alcohol consumption in Scotland. Here, we update findings by using more recent data and by quantifying emergent biases. Underestimation resulting from the net effect of biases on population consumption in Scotland increased from -4% in 2010 to -7% in 2013. Biases that might impact on the validity and reliability of sales data when estimating population consumption should be routinely monitored and updated. © The Author 2015. Medical Council on Alcohol and Oxford University Press.

Tracking Biases: An Update to the Validity and Reliability of Alcohol Retail Sales Data for Estimating Population Consumption in Scotland

PubMed Central

Henderson, Audrey; Robinson, Mark; McAdams, Rachel; McCartney, Gerry; Beeston, Clare

2016-01-01

Aims To highlight the importance of monitoring biases when using retail sales data to estimate population alcohol consumption. Methods Previously, we identified and where possible quantified sources of bias that may lead to under- or overestimation of alcohol consumption in Scotland. Here, we update findings by using more recent data and by quantifying emergent biases. Results Underestimation resulting from the net effect of biases on population consumption in Scotland increased from −4% in 2010 to −7% in 2013. Conclusion Biases that might impact on the validity and reliability of sales data when estimating population consumption should be routinely monitored and updated. PMID:26419684

Reliability Modeling of Microelectromechanical Systems Using Neural Networks

NASA Technical Reports Server (NTRS)

Perera. J. Sebastian

2000-01-01

Microelectromechanical systems (MEMS) are a broad and rapidly expanding field that is currently receiving a great deal of attention because of the potential to significantly improve the ability to sense, analyze, and control a variety of processes, such as heating and ventilation systems, automobiles, medicine, aeronautical flight, military surveillance, weather forecasting, and space exploration. MEMS are very small and are a blend of electrical and mechanical components, with electrical and mechanical systems on one chip. This research establishes reliability estimation and prediction for MEMS devices at the conceptual design phase using neural networks. At the conceptual design phase, before devices are built and tested, traditional methods of quantifying reliability are inadequate because the device is not in existence and cannot be tested to establish the reliability distributions. A novel approach using neural networks is created to predict the overall reliability of a MEMS device based on its components and each component's attributes. The methodology begins with collecting attribute data (fabrication process, physical specifications, operating environment, property characteristics, packaging, etc.) and reliability data for many types of microengines. The data are partitioned into training data (the majority) and validation data (the remainder). A neural network is applied to the training data (both attribute and reliability); the attributes become the system inputs and reliability data (cycles to failure), the system output. After the neural network is trained with sufficient data. the validation data are used to verify the neural networks provided accurate reliability estimates. Now, the reliability of a new proposed MEMS device can be estimated by using the appropriate trained neural networks developed in this work.

Predicting Cost/Reliability/Maintainability of Advanced General Aviation Avionics Equipment

NASA Technical Reports Server (NTRS)

Davis, M. R.; Kamins, M.; Mooz, W. E.

1978-01-01

A methodology is provided for assisting NASA in estimating the cost, reliability, and maintenance (CRM) requirements for general avionics equipment operating in the 1980's. Practical problems of predicting these factors are examined. The usefulness and short comings of different approaches for modeling coast and reliability estimates are discussed together with special problems caused by the lack of historical data on the cost of maintaining general aviation avionics. Suggestions are offered on how NASA might proceed in assessing cost reliability CRM implications in the absence of reliable generalized predictive models.

Probability based remaining capacity estimation using data-driven and neural network model

NASA Astrophysics Data System (ADS)

Wang, Yujie; Yang, Duo; Zhang, Xu; Chen, Zonghai

2016-05-01

Since large numbers of lithium-ion batteries are composed in pack and the batteries are complex electrochemical devices, their monitoring and safety concerns are key issues for the applications of battery technology. An accurate estimation of battery remaining capacity is crucial for optimization of the vehicle control, preventing battery from over-charging and over-discharging and ensuring the safety during its service life. The remaining capacity estimation of a battery includes the estimation of state-of-charge (SOC) and state-of-energy (SOE). In this work, a probability based adaptive estimator is presented to obtain accurate and reliable estimation results for both SOC and SOE. For the SOC estimation, an n ordered RC equivalent circuit model is employed by combining an electrochemical model to obtain more accurate voltage prediction results. For the SOE estimation, a sliding window neural network model is proposed to investigate the relationship between the terminal voltage and the model inputs. To verify the accuracy and robustness of the proposed model and estimation algorithm, experiments under different dynamic operation current profiles are performed on the commercial 1665130-type lithium-ion batteries. The results illustrate that accurate and robust estimation can be obtained by the proposed method.

Assessing Interval Estimation Methods for Hill Model ...

EPA Pesticide Factsheets

The Hill model of concentration-response is ubiquitous in toxicology, perhaps because its parameters directly relate to biologically significant metrics of toxicity such as efficacy and potency. Point estimates of these parameters obtained through least squares regression or maximum likelihood are commonly used in high-throughput risk assessment, but such estimates typically fail to include reliable information concerning confidence in (or precision of) the estimates. To address this issue, we examined methods for assessing uncertainty in Hill model parameter estimates derived from concentration-response data. In particular, using a sample of ToxCast concentration-response data sets, we applied four methods for obtaining interval estimates that are based on asymptotic theory, bootstrapping (two varieties), and Bayesian parameter estimation, and then compared the results. These interval estimation methods generally did not agree, so we devised a simulation study to assess their relative performance. We generated simulated data by constructing four statistical error models capable of producing concentration-response data sets comparable to those observed in ToxCast. We then applied the four interval estimation methods to the simulated data and compared the actual coverage of the interval estimates to the nominal coverage (e.g., 95%) in order to quantify performance of each of the methods in a variety of cases (i.e., different values of the true Hill model paramet

Estimating Infection Attack Rates and Severity in Real Time during an Influenza Pandemic: Analysis of Serial Cross-Sectional Serologic Surveillance Data

PubMed Central

Wu, Joseph T.; Ho, Andrew; Ma, Edward S. K.; Lee, Cheuk Kwong; Chu, Daniel K. W.; Ho, Po-Lai; Hung, Ivan F. N.; Ho, Lai Ming; Lin, Che Kit; Tsang, Thomas; Lo, Su-Vui; Lau, Yu-Lung; Leung, Gabriel M.

2011-01-01

Background In an emerging influenza pandemic, estimating severity (the probability of a severe outcome, such as hospitalization, if infected) is a public health priority. As many influenza infections are subclinical, sero-surveillance is needed to allow reliable real-time estimates of infection attack rate (IAR) and severity. Methods and Findings We tested 14,766 sera collected during the first wave of the 2009 pandemic in Hong Kong using viral microneutralization. We estimated IAR and infection-hospitalization probability (IHP) from the serial cross-sectional serologic data and hospitalization data. Had our serologic data been available weekly in real time, we would have obtained reliable IHP estimates 1 wk after, 1–2 wk before, and 3 wk after epidemic peak for individuals aged 5–14 y, 15–29 y, and 30–59 y. The ratio of IAR to pre-existing seroprevalence, which decreased with age, was a major determinant for the timeliness of reliable estimates. If we began sero-surveillance 3 wk after community transmission was confirmed, with 150, 350, and 500 specimens per week for individuals aged 5–14 y, 15–19 y, and 20–29 y, respectively, we would have obtained reliable IHP estimates for these age groups 4 wk before the peak. For 30–59 y olds, even 800 specimens per week would not have generated reliable estimates until the peak because the ratio of IAR to pre-existing seroprevalence for this age group was low. The performance of serial cross-sectional sero-surveillance substantially deteriorates if test specificity is not near 100% or pre-existing seroprevalence is not near zero. These potential limitations could be mitigated by choosing a higher titer cutoff for seropositivity. If the epidemic doubling time is longer than 6 d, then serial cross-sectional sero-surveillance with 300 specimens per week would yield reliable estimates when IAR reaches around 6%–10%. Conclusions Serial cross-sectional serologic data together with clinical surveillance data can

Tactile Acuity Charts: A Reliable Measure of Spatial Acuity

PubMed Central

Bruns, Patrick; Camargo, Carlos J.; Campanella, Humberto; Esteve, Jaume; Dinse, Hubert R.; Röder, Brigitte

2014-01-01

For assessing tactile spatial resolution it has recently been recommended to use tactile acuity charts which follow the design principles of the Snellen letter charts for visual acuity and involve active touch. However, it is currently unknown whether acuity thresholds obtained with this newly developed psychophysical procedure are in accordance with established measures of tactile acuity that involve passive contact with fixed duration and control of contact force. Here we directly compared tactile acuity thresholds obtained with the acuity charts to traditional two-point and grating orientation thresholds in a group of young healthy adults. For this purpose, two types of charts, using either Braille-like dot patterns or embossed Landolt rings with different orientations, were adapted from previous studies. Measurements with the two types of charts were equivalent, but generally more reliable with the dot pattern chart. A comparison with the two-point and grating orientation task data showed that the test-retest reliability of the acuity chart measurements after one week was superior to that of the passive methods. Individual thresholds obtained with the acuity charts agreed reasonably with the grating orientation threshold, but less so with the two-point threshold that yielded relatively distinct acuity estimates compared to the other methods. This potentially considerable amount of mismatch between different measures of tactile acuity suggests that tactile spatial resolution is a complex entity that should ideally be measured with different methods in parallel. The simple test procedure and high reliability of the acuity charts makes them a promising complement and alternative to the traditional two-point and grating orientation thresholds. PMID:24504346

Tracking reliability for space cabin-borne equipment in development by Crow model.

PubMed

Chen, J D; Jiao, S J; Sun, H L

2001-12-01

Objective. To study and track the reliability growth of manned spaceflight cabin-borne equipment in the course of its development. Method. A new technique of reliability growth estimation and prediction, which is composed of the Crow model and test data conversion (TDC) method was used. Result. The estimation and prediction value of the reliability growth conformed to its expectations. Conclusion. The method could dynamically estimate and predict the reliability of the equipment by making full use of various test information in the course of its development. It offered not only a possibility of tracking the equipment reliability growth, but also the reference for quality control in manned spaceflight cabin-borne equipment design and development process.

A Meta-Analysis of Reliability Coefficients in Second Language Research

ERIC Educational Resources Information Center

Plonsky, Luke; Derrick, Deirdre J.

2016-01-01

Ensuring internal validity in quantitative research requires, among other conditions, reliable instrumentation. Unfortunately, however, second language (L2) researchers often fail to report and even more often fail to interpret reliability estimates beyond generic benchmarks for acceptability. As a means to guide interpretations of such estimates,…

Assessment of the reliability of human corneal endothelial cell-density estimates using a noncontact specular microscope.

PubMed

Doughty, M J; Müller, A; Zaman, M L

2000-03-01

We sought to determine the variance in endothelial cell density (ECD) estimates for human corneal endothelia. Noncontact specular micrographs were obtained from white subjects without any history of contact lens wear, or major eye disease or surgery; subjects were within four age groups (children, young adults, older adults, senior citizens). The endothelial image was scanned, and the areas from > or =75 cells measured from an overlay by planimetry. The cell-area values were used to calculate the ECD repeatedly so that the intra- and intersubject variation in an average ECD estimate could be made by using different numbers of cells (5, 10, 15, etc.). An average ECD of 3,519 cells/mm2 (range, 2,598-5,312 cells/mm2) was obtained of counts of 75 cells/ endothelium from individuals aged 6-83 years. Average ECD estimates in each age group were 4,124, 3,457, 3,360, and 3,113 cells/mm2, respectively. Analysis of intersubject variance revealed that ECD estimates would be expected to be no better than +/-10% if only 25 cells were measured per endothelium, but approach +/-2% if 75 cells are measured. In assessing the corneal endothelium by noncontact specular microscopy, cell count should be given, and this should be > or =75/ endothelium for an expected variance to be at a level close to that recommended for monitoring age-, stress-, or surgery-related changes.

Methodology for Software Reliability Prediction. Volume 1.

DTIC Science & Technology

1987-11-01

SPACECRAFT 0 MANNED SPACECRAFT B ATCH SYSTEM AIRBORNE AVIONICS 0 UNMANNED EVENT C014TROL a REAL TIME CLOSED 0 UNMANNED SPACECRAFT LOOP OPERATINS SPACECRAFT...software reliability. A Software Reliability Measurement Framework was established which spans the life cycle of a software system and includes the...specification, prediction, estimation, and assessment of software reliability. Data from 59 systems , representing over 5 million lines of code, were

Visual judgements of steadiness in one-legged stance: reliability and validity.

PubMed

Haupstein, T; Goldie, P

2000-01-01

There is a paucity of information about the validity and reliability of clinicians' visual judgements of steadiness in one-legged stance. Such judgements are used frequently in clinical practice to support decisions about treatment in the fields of neurology, sports medicine, paediatrics and orthopaedics. The aim of the present study was to address the validity and reliability of visual judgements of steadiness in one-legged stance in a group of physiotherapists. A videotape of 20 five-second performances was shown to 14 physiotherapists with median clinical experience of 6.75 years. Validity of visual judgement was established by correlating scores obtained from an 11-point rating scale with criterion scores obtained from a force platform. In addition, partial correlations were used to control for the potential influence of body weight on the relationship between the visual judgements and criterion scores. Inter-observer reliability was quantified between the physiotherapists; intra-observer reliability was quantified between two tests four weeks apart. Mean criterion-related validity was high, regardless of whether body weight was controlled for statistically (Pearson's r = 0.84, 0.83, respectively). The standard error of estimating the criterion score was 3.3 newtons. Inter-observer reliability was high (ICC (2,1) = 0.81 at Test 1 and 0.82 at Test 2). Intra-observer reliability was high (on average ICC (2,1) = 0.88; Pearson's r = 0.90). The standard error of measurement for the 11-point scale was one unit. The finding of higher accuracy of making visual judgements than previously reported may be due to several aspects of design: use of a criterion score derived from the variability of the force signal which is more discriminating than variability of centre of pressure; use of a discriminating visual rating scale; specificity and clear definition of the phenomenon to be rated.

A study of fault prediction and reliability assessment in the SEL environment

NASA Technical Reports Server (NTRS)

Basili, Victor R.; Patnaik, Debabrata

1986-01-01

An empirical study on estimation and prediction of faults, prediction of fault detection and correction effort, and reliability assessment in the Software Engineering Laboratory environment (SEL) is presented. Fault estimation using empirical relationships and fault prediction using curve fitting method are investigated. Relationships between debugging efforts (fault detection and correction effort) in different test phases are provided, in order to make an early estimate of future debugging effort. This study concludes with the fault analysis, application of a reliability model, and analysis of a normalized metric for reliability assessment and reliability monitoring during development of software.

A Model for Estimating the Reliability and Validity of Criterion-Referenced Measures.

ERIC Educational Resources Information Center

Edmonston, Leon P.; Randall, Robert S.

A decision model designed to determine the reliability and validity of criterion referenced measures (CRMs) is presented. General procedures which pertain to the model are discussed as to: Measures of relationship, Reliability, Validity (content, criterion-oriented, and construct validation), and Item Analysis. The decision model is presented in…

Minimum number of days required for a reliable estimate of daily step count and energy expenditure, in people with MS who walk unaided.

PubMed

Norris, Michelle; Anderson, Ross; Motl, Robert W; Hayes, Sara; Coote, Susan

2017-03-01

The purpose of this study was to examine the minimum number of days needed to reliably estimate daily step count and energy expenditure (EE), in people with multiple sclerosis (MS) who walked unaided. Seven days of activity monitor data were collected for 26 participants with MS (age=44.5±11.9years; time since diagnosis=6.5±6.2years; Patient Determined Disease Steps=≤3). Mean daily step count and mean daily EE (kcal) were calculated for all combinations of days (127 combinations), and compared to the respective 7-day mean daily step count or mean daily EE using intra-class correlations (ICC), the Generalizability Theory and Bland-Altman. For step count, ICC values of 0.94-0.98 and a G-coefficient of 0.81 indicate a minimum of any random 2-day combination is required to reliably calculate mean daily step count. For EE, ICC values of 0.96-0.99 and a G-coefficient of 0.83 indicate a minimum of any random 4-day combination is required to reliably calculate mean daily EE. For Bland-Altman analyses all combinations of days, bar single day combinations, resulted in a mean bias within ±10%, when expressed as a percentage of the 7-day mean daily step count or mean daily EE. A minimum of 2days for step count and 4days for EE, regardless of day type, is needed to reliably estimate daily step count and daily EE, in people with MS who walk unaided. Copyright © 2017 Elsevier B.V. All rights reserved.

Approximation of reliabilities for multiple-trait model with maternal effects.

PubMed

Strabel, T; Misztal, I; Bertrand, J K

2001-04-01

Reliabilities for a multiple-trait maternal model were obtained by combining reliabilities obtained from single-trait models. Single-trait reliabilities were obtained using an approximation that supported models with additive and permanent environmental effects. For the direct effect, the maternal and permanent environmental variances were assigned to the residual. For the maternal effect, variance of the direct effect was assigned to the residual. Data included 10,550 birth weight, 11,819 weaning weight, and 3,617 postweaning gain records of Senepol cattle. Reliabilities were obtained by generalized inversion and by using single-trait and multiple-trait approximation methods. Some reliabilities obtained by inversion were negative because inbreeding was ignored in calculating the inverse of the relationship matrix. The multiple-trait approximation method reduced the bias of approximation when compared with the single-trait method. The correlations between reliabilities obtained by inversion and by multiple-trait procedures for the direct effect were 0.85 for birth weight, 0.94 for weaning weight, and 0.96 for postweaning gain. Correlations for maternal effects for birth weight and weaning weight were 0.96 to 0.98 for both approximations. Further improvements can be achieved by refining the single-trait procedures.

The application of emulation techniques in the analysis of highly reliable, guidance and control computer systems

NASA Technical Reports Server (NTRS)

Migneault, Gerard E.

1987-01-01

Emulation techniques can be a solution to a difficulty that arises in the analysis of the reliability of guidance and control computer systems for future commercial aircraft. Described here is the difficulty, the lack of credibility of reliability estimates obtained by analytical modeling techniques. The difficulty is an unavoidable consequence of the following: (1) a reliability requirement so demanding as to make system evaluation by use testing infeasible; (2) a complex system design technique, fault tolerance; (3) system reliability dominated by errors due to flaws in the system definition; and (4) elaborate analytical modeling techniques whose precision outputs are quite sensitive to errors of approximation in their input data. Use of emulation techniques for pseudo-testing systems to evaluate bounds on the parameter values needed for the analytical techniques is then discussed. Finally several examples of the application of emulation techniques are described.

Accuracy of a Classical Test Theory-Based Procedure for Estimating the Reliability of a Multistage Test. Research Report. ETS RR-17-02

ERIC Educational Resources Information Center

Kim, Sooyeon; Livingston, Samuel A.

2017-01-01

The purpose of this simulation study was to assess the accuracy of a classical test theory (CTT)-based procedure for estimating the alternate-forms reliability of scores on a multistage test (MST) having 3 stages. We generated item difficulty and discrimination parameters for 10 parallel, nonoverlapping forms of the complete 3-stage test and…

Quantified Risk Ranking Model for Condition-Based Risk and Reliability Centered Maintenance

NASA Astrophysics Data System (ADS)

Chattopadhyaya, Pradip Kumar; Basu, Sushil Kumar; Majumdar, Manik Chandra

2017-06-01

In the recent past, risk and reliability centered maintenance (RRCM) framework is introduced with a shift in the methodological focus from reliability and probabilities (expected values) to reliability, uncertainty and risk. In this paper authors explain a novel methodology for risk quantification and ranking the critical items for prioritizing the maintenance actions on the basis of condition-based risk and reliability centered maintenance (CBRRCM). The critical items are identified through criticality analysis of RPN values of items of a system and the maintenance significant precipitating factors (MSPF) of items are evaluated. The criticality of risk is assessed using three risk coefficients. The likelihood risk coefficient treats the probability as a fuzzy number. The abstract risk coefficient deduces risk influenced by uncertainty, sensitivity besides other factors. The third risk coefficient is called hazardous risk coefficient, which is due to anticipated hazards which may occur in the future and the risk is deduced from criteria of consequences on safety, environment, maintenance and economic risks with corresponding cost for consequences. The characteristic values of all the three risk coefficients are obtained with a particular test. With few more tests on the system, the values may change significantly within controlling range of each coefficient, hence `random number simulation' is resorted to obtain one distinctive value for each coefficient. The risk coefficients are statistically added to obtain final risk coefficient of each critical item and then the final rankings of critical items are estimated. The prioritization in ranking of critical items using the developed mathematical model for risk assessment shall be useful in optimization of financial losses and timing of maintenance actions.

Reliability analysis of component of affination centrifugal 1 machine by using reliability engineering

NASA Astrophysics Data System (ADS)

Sembiring, N.; Ginting, E.; Darnello, T.

2017-12-01

Problems that appear in a company that produces refined sugar, the production floor has not reached the level of critical machine availability because it often suffered damage (breakdown). This results in a sudden loss of production time and production opportunities. This problem can be solved by Reliability Engineering method where the statistical approach to historical damage data is performed to see the pattern of the distribution. The method can provide a value of reliability, rate of damage, and availability level, of an machine during the maintenance time interval schedule. The result of distribution test to time inter-damage data (MTTF) flexible hose component is lognormal distribution while component of teflon cone lifthing is weibull distribution. While from distribution test to mean time of improvement (MTTR) flexible hose component is exponential distribution while component of teflon cone lifthing is weibull distribution. The actual results of the flexible hose component on the replacement schedule per 720 hours obtained reliability of 0.2451 and availability 0.9960. While on the critical components of teflon cone lifthing actual on the replacement schedule per 1944 hours obtained reliability of 0.4083 and availability 0.9927.

Traveling-wave tube reliability estimates, life tests, and space flight experience

NASA Technical Reports Server (NTRS)

Lalli, V. R.; Speck, C. E.

1977-01-01

Infant mortality, useful life, and wearout phase of twt life are considered. The performance of existing developmental tubes, flight experience, and sequential hardware testing are evaluated. The reliability history of twt's in space applications is documented by considering: (1) the generic parts of the tube in light of the manner in which their design and operation affect the ultimate reliability of the device, (2) the flight experience of medium power tubes, and (3) the available life test data for existing space-qualified twt's in addition to those of high power devices.

Measuring eating disorder attitudes and behaviors: a reliability generalization study

PubMed Central

2014-01-01

Background Although score reliability is a sample-dependent characteristic, researchers often only report reliability estimates from previous studies as justification for employing particular questionnaires in their research. The present study followed reliability generalization procedures to determine the mean score reliability of the Eating Disorder Inventory and its most commonly employed subscales (Drive for Thinness, Bulimia, and Body Dissatisfaction) and the Eating Attitudes Test as a way to better identify those characteristics that might impact score reliability. Methods Published studies that used these measures were coded based on their reporting of reliability information and additional study characteristics that might influence score reliability. Results Score reliability estimates were included in 26.15% of studies using the EDI and 36.28% of studies using the EAT. Mean Cronbach’s alphas for the EDI (total score = .91; subscales = .75 to .89), EAT-40 (total score = .81) and EAT-26 (total score = .86; subscales = .56 to .80) suggested variability in estimated internal consistency. Whereas some EDI subscales exhibited higher score reliability in clinical eating disorder samples than in nonclinical samples, other subscales did not exhibit these differences. Score reliability information for the EAT was primarily reported for nonclinical samples, making it difficult to characterize the effect of type of sample on these measures. However, there was a tendency for mean score reliability to be higher in the adult (vs. adolescent) samples and in female (vs. male) samples. Conclusions Overall, this study highlights the importance of assessing and reporting internal consistency during every test administration because reliability is affected by characteristics of the participants being examined. PMID:24764530

Validity and reliability of dental age estimation of teeth root translucency based on digital luminance determination.

PubMed

Ramsthaler, Frank; Kettner, Mattias; Verhoff, Marcel A

2014-01-01

In forensic anthropological casework, estimating age-at-death is key to profiling unknown skeletal remains. The aim of this study was to examine the reliability of a new, simple, fast, and inexpensive digital odontological method for age-at-death estimation. The method is based on the original Lamendin method, which is a widely used technique in the repertoire of odontological aging methods in forensic anthropology. We examined 129 single root teeth employing a digital camera and imaging software for the measurement of the luminance of the teeth's translucent root zone. Variability in luminance detection was evaluated using statistical technical error of measurement analysis. The method revealed stable values largely unrelated to observer experience, whereas requisite formulas proved to be camera-specific and should therefore be generated for an individual recording setting based on samples of known chronological age. Multiple regression analysis showed a highly significant influence of the coefficients of the variables "arithmetic mean" and "standard deviation" of luminance for the regression formula. For the use of this primer multivariate equation for age-at-death estimation in casework, a standard error of the estimate of 6.51 years was calculated. Step-by-step reduction of the number of embedded variables to linear regression analysis employing the best contributor "arithmetic mean" of luminance yielded a regression equation with a standard error of 6.72 years (p < 0.001). The results of this study not only support the premise of root translucency as an age-related phenomenon, but also demonstrate that translucency reflects a number of other influencing factors in addition to age. This new digital measuring technique of the zone of dental root luminance can broaden the array of methods available for estimating chronological age, and furthermore facilitate measurement and age classification due to its low dependence on observer experience.

Coefficient Alpha and Reliability of Scale Scores

ERIC Educational Resources Information Center

Almehrizi, Rashid S.

2013-01-01

The majority of large-scale assessments develop various score scales that are either linear or nonlinear transformations of raw scores for better interpretations and uses of assessment results. The current formula for coefficient alpha (a; the commonly used reliability coefficient) only provides internal consistency reliability estimates of raw…

The probability estimation of the electronic lesson implementation taking into account software reliability

NASA Astrophysics Data System (ADS)

Gurov, V. V.

2017-01-01

Software tools for educational purposes, such as e-lessons, computer-based testing system, from the point of view of reliability, have a number of features. The main ones among them are the need to ensure a sufficiently high probability of their faultless operation for a specified time, as well as the impossibility of their rapid recovery by the way of replacing it with a similar running program during the classes. The article considers the peculiarities of reliability evaluation of programs in contrast to assessments of hardware reliability. The basic requirements to reliability of software used for carrying out practical and laboratory classes in the form of computer-based training programs are given. The essential requirements applicable to the reliability of software used for conducting the practical and laboratory studies in the form of computer-based teaching programs are also described. The mathematical tool based on Markov chains, which allows to determine the degree of debugging of the training program for use in the educational process by means of applying the graph of the software modules interaction, is presented.

An Automated Technique for Estimating Daily Precipitation over the State of Virginia

NASA Technical Reports Server (NTRS)

Follansbee, W. A.; Chamberlain, L. W., III

1981-01-01

Digital IR and visible imagery obtained from a geostationary satellite located over the equator at 75 deg west latitude were provided by NASA and used to obtain a linear relationship between cloud top temperature and hourly precipitation. Two computer programs written in FORTRAN were used. The first program computes the satellite estimate field from the hourly digital IR imagery. The second program computes the final estimate for the entire state area by comparing five preliminary estimates of 24 hour precipitation with control raingage readings and determining which of the five methods gives the best estimate for the day. The final estimate is then produced by incorporating control gage readings into the winning method. In presenting reliable precipitation estimates for every cell in Virginia in near real time on a daily on going basis, the techniques require on the order of 125 to 150 daily gage readings by dependable, highly motivated observers distributed as uniformly as feasible across the state.

Fully decentralized estimation and control for a modular wheeled mobile robot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mutambara, A.G.O.; Durrant-Whyte, H.F.

2000-06-01

In this paper, the problem of fully decentralized data fusion and control for a modular wheeled mobile robot (WMR) is addressed. This is a vehicle system with nonlinear kinematics, distributed multiple sensors, and nonlinear sensor models. The problem is solved by applying fully decentralized estimation and control algorithms based on the extended information filter. This is achieved by deriving a modular, decentralized kinematic model by using plane motion kinematics to obtain the forward and inverse kinematics for a generalized simple wheeled vehicle. This model is then used in the decentralized estimation and control algorithms. WMR estimation and control is thusmore » obtained locally using reduced order models with reduced communication of information between nodes is carried out after every measurement (full rate communication), the estimates and control signals obtained at each node are equivalent to those obtained by a corresponding centralized system. Transputer architecture is used as the basis for hardware and software design as it supports the extensive communication and concurrency requirements that characterize modular and decentralized systems. The advantages of a modular WMR vehicle include scalability, application flexibility, low prototyping costs, and high reliability.« less

PREDICTION OF RELIABILITY IN BIOGRAPHICAL QUESTIONNAIRES.

ERIC Educational Resources Information Center

STARRY, ALLAN R.

THE OBJECTIVES OF THIS STUDY WERE (1) TO DEVELOP A GENERAL CLASSIFICATION SYSTEM FOR LIFE HISTORY ITEMS, (2) TO DETERMINE TEST-RETEST RELIABILITY ESTIMATES, AND (3) TO ESTIMATE RESISTANCE TO EXAMINEE FAKING, FOR REPRESENTATIVE BIOGRAPHICAL QUESTIONNAIRES. TWO 100-ITEM QUESTIONNAIRES WERE CONSTRUCTED THROUGH RANDOM ASSIGNMENT BY CONTENT AREA OF 200…

Constructing the 'Best' Reliability Data for the Job - Developing Generic Reliability Data from Alternative Sources Early in a Product's Development Phase

NASA Technical Reports Server (NTRS)

Kleinhammer, Roger K.; Graber, Robert R.; DeMott, D. L.

2016-01-01

Reliability practitioners advocate getting reliability involved early in a product development process. However, when assigned to estimate or assess the (potential) reliability of a product or system early in the design and development phase, they are faced with lack of reasonable models or methods for useful reliability estimation. Developing specific data is costly and time consuming. Instead, analysts rely on available data to assess reliability. Finding data relevant to the specific use and environment for any project is difficult, if not impossible. Instead, analysts attempt to develop the "best" or composite analog data to support the assessments. Industries, consortia and vendors across many areas have spent decades collecting, analyzing and tabulating fielded item and component reliability performance in terms of observed failures and operational use. This data resource provides a huge compendium of information for potential use, but can also be compartmented by industry, difficult to find out about, access, or manipulate. One method used incorporates processes for reviewing these existing data sources and identifying the available information based on similar equipment, then using that generic data to derive an analog composite. Dissimilarities in equipment descriptions, environment of intended use, quality and even failure modes impact the "best" data incorporated in an analog composite. Once developed, this composite analog data provides a "better" representation of the reliability of the equipment or component. It can be used to support early risk or reliability trade studies, or analytical models to establish the predicted reliability data points. It also establishes a baseline prior that may updated based on test data or observed operational constraints and failures, i.e., using Bayesian techniques. This tutorial presents a descriptive compilation of historical data sources across numerous industries and disciplines, along with examples of contents

Operation Reliability Assessment for Cutting Tools by Applying a Proportional Covariate Model to Condition Monitoring Information

PubMed Central

Cai, Gaigai; Chen, Xuefeng; Li, Bing; Chen, Baojia; He, Zhengjia

2012-01-01

The reliability of cutting tools is critical to machining precision and production efficiency. The conventional statistic-based reliability assessment method aims at providing a general and overall estimation of reliability for a large population of identical units under given and fixed conditions. However, it has limited effectiveness in depicting the operational characteristics of a cutting tool. To overcome this limitation, this paper proposes an approach to assess the operation reliability of cutting tools. A proportional covariate model is introduced to construct the relationship between operation reliability and condition monitoring information. The wavelet packet transform and an improved distance evaluation technique are used to extract sensitive features from vibration signals, and a covariate function is constructed based on the proportional covariate model. Ultimately, the failure rate function of the cutting tool being assessed is calculated using the baseline covariate function obtained from a small sample of historical data. Experimental results and a comparative study show that the proposed method is effective for assessing the operation reliability of cutting tools. PMID:23201980

Comparison of internal dose estimates obtained using organ-level, voxel S value, and Monte Carlo techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grimes, Joshua, E-mail: grimes.joshua@mayo.edu; Celler, Anna

2014-09-15

Purpose: The authors’ objective was to compare internal dose estimates obtained using the Organ Level Dose Assessment with Exponential Modeling (OLINDA/EXM) software, the voxel S value technique, and Monte Carlo simulation. Monte Carlo dose estimates were used as the reference standard to assess the impact of patient-specific anatomy on the final dose estimate. Methods: Six patients injected with{sup 99m}Tc-hydrazinonicotinamide-Tyr{sup 3}-octreotide were included in this study. A hybrid planar/SPECT imaging protocol was used to estimate {sup 99m}Tc time-integrated activity coefficients (TIACs) for kidneys, liver, spleen, and tumors. Additionally, TIACs were predicted for {sup 131}I, {sup 177}Lu, and {sup 90}Y assuming themore » same biological half-lives as the {sup 99m}Tc labeled tracer. The TIACs were used as input for OLINDA/EXM for organ-level dose calculation and voxel level dosimetry was performed using the voxel S value method and Monte Carlo simulation. Dose estimates for {sup 99m}Tc, {sup 131}I, {sup 177}Lu, and {sup 90}Y distributions were evaluated by comparing (i) organ-level S values corresponding to each method, (ii) total tumor and organ doses, (iii) differences in right and left kidney doses, and (iv) voxelized dose distributions calculated by Monte Carlo and the voxel S value technique. Results: The S values for all investigated radionuclides used by OLINDA/EXM and the corresponding patient-specific S values calculated by Monte Carlo agreed within 2.3% on average for self-irradiation, and differed by as much as 105% for cross-organ irradiation. Total organ doses calculated by OLINDA/EXM and the voxel S value technique agreed with Monte Carlo results within approximately ±7%. Differences between right and left kidney doses determined by Monte Carlo were as high as 73%. Comparison of the Monte Carlo and voxel S value dose distributions showed that each method produced similar dose volume histograms with a minimum dose covering 90% of the volume

The Assumption of a Reliable Instrument and Other Pitfalls to Avoid When Considering the Reliability of Data

PubMed Central

Nimon, Kim; Zientek, Linda Reichwein; Henson, Robin K.

2012-01-01

The purpose of this article is to help researchers avoid common pitfalls associated with reliability including incorrectly assuming that (a) measurement error always attenuates observed score correlations, (b) different sources of measurement error originate from the same source, and (c) reliability is a function of instrumentation. To accomplish our purpose, we first describe what reliability is and why researchers should care about it with focus on its impact on effect sizes. Second, we review how reliability is assessed with comment on the consequences of cumulative measurement error. Third, we consider how researchers can use reliability generalization as a prescriptive method when designing their research studies to form hypotheses about whether or not reliability estimates will be acceptable given their sample and testing conditions. Finally, we discuss options that researchers may consider when faced with analyzing unreliable data. PMID:22518107

Reliability of Nationwide Prevalence Estimates of Dementia: A Critical Appraisal Based on Brazilian Surveys

PubMed Central

2015-01-01

Background The nationwide dementia prevalence is usually calculated by applying the results of local surveys to countries’ populations. To evaluate the reliability of such estimations in developing countries, we chose Brazil as an example. We carried out a systematic review of dementia surveys, ascertained their risk of bias, and present the best estimate of occurrence of dementia in Brazil. Methods and Findings We carried out an electronic search of PubMed, Latin-American databases, and a Brazilian thesis database for surveys focusing on dementia prevalence in Brazil. The systematic review was registered at PROSPERO (CRD42014008815). Among the 35 studies found, 15 analyzed population-based random samples. However, most of them utilized inadequate criteria for diagnostics. Six studies without these limitations were further analyzed to assess the risk of selection, attrition, outcome and population bias as well as several statistical issues. All the studies presented moderate or high risk of bias in at least two domains due to the following features: high non-response, inaccurate cut-offs, and doubtful accuracy of the examiners. Two studies had limited external validity due to high rates of illiteracy or low income. The three studies with adequate generalizability and the lowest risk of bias presented a prevalence of dementia between 7.1% and 8.3% among subjects aged 65 years and older. However, after adjustment for accuracy of screening, the best available evidence points towards a figure between 15.2% and 16.3%. Conclusions The risk of bias may strongly limit the generalizability of dementia prevalence estimates in developing countries. Extrapolations that have already been made for Brazil and Latin America were based on a prevalence that should have been adjusted for screening accuracy or not used at all due to severe bias. Similar evaluations regarding other developing countries are needed in order to verify the scope of these limitations. PMID:26131563

Measurement and Reliability of Response Inhibition

PubMed Central

Congdon, Eliza; Mumford, Jeanette A.; Cohen, Jessica R.; Galvan, Adriana; Canli, Turhan; Poldrack, Russell A.

2012-01-01

Response inhibition plays a critical role in adaptive functioning and can be assessed with the Stop-signal task, which requires participants to suppress prepotent motor responses. Evidence suggests that this ability to inhibit a prepotent motor response (reflected as Stop-signal reaction time (SSRT)) is a quantitative and heritable measure of interindividual variation in brain function. Although attention has been given to the optimal method of SSRT estimation, and initial evidence exists in support of its reliability, there is still variability in how Stop-signal task data are treated across samples. In order to examine this issue, we pooled data across three separate studies and examined the influence of multiple SSRT calculation methods and outlier calling on reliability (using Intra-class correlation). Our results suggest that an approach which uses the average of all available sessions, all trials of each session, and excludes outliers based on predetermined lenient criteria yields reliable SSRT estimates, while not excluding too many participants. Our findings further support the reliability of SSRT, which is commonly used as an index of inhibitory control, and provide support for its continued use as a neurocognitive phenotype. PMID:22363308

Comparing reliabilities of strip and conventional patch testing.

PubMed

Dickel, Heinrich; Geier, Johannes; Kreft, Burkhard; Pfützner, Wolfgang; Kuss, Oliver

2017-06-01

The standardized protocol for performing the strip patch test has proven to be valid, but evidence on its reliability is still missing. To estimate the parallel-test reliability of the strip patch test as compared with the conventional patch test. In this multicentre, prospective, randomized, investigator-blinded reliability study, 132 subjects were enrolled. Simultaneous duplicate strip and conventional patch tests were performed with the Finn Chambers ® on Scanpor ® tape test system and the patch test preparations nickel sulfate 5% pet., potassium dichromate 0.5% pet., and lanolin alcohol 30% pet. Reliability was estimated by the use of Cohen's kappa coefficient. Parallel-test reliability values of the three standard patch test preparations turned out to be acceptable, with slight advantages for the strip patch test. The differences in reliability were 9% (95%CI: -8% to 26%) for nickel sulfate and 23% (95%CI: -16% to 63%) for potassium dichromate, both favouring the strip patch test. The standardized strip patch test method for the detection of allergic contact sensitization in patients with suspected allergic contact dermatitis is reliable. Its application in routine clinical practice can be recommended, especially if the conventional patch test result is presumably false negative. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The Challenges of Credible Thermal Protection System Reliability Quantification

NASA Technical Reports Server (NTRS)

Green, Lawrence L.

2013-01-01

The paper discusses several of the challenges associated with developing a credible reliability estimate for a human-rated crew capsule thermal protection system. The process of developing such a credible estimate is subject to the quantification, modeling and propagation of numerous uncertainties within a probabilistic analysis. The development of specific investment recommendations, to improve the reliability prediction, among various potential testing and programmatic options is then accomplished through Bayesian analysis.

Comparison of GPS receiver DCB estimation methods using a GPS network

NASA Astrophysics Data System (ADS)

Choi, Byung-Kyu; Park, Jong-Uk; Min Roh, Kyoung; Lee, Sang-Jeong

2013-07-01

Two approaches for receiver differential code biases (DCB) estimation using the GPS data obtained from the Korean GPS network (KGN) in South Korea are suggested: the relative and single (absolute) methods. The relative method uses a GPS network, while the single method determines DCBs from a single station only. Their performance was assessed by comparing the receiver DCB values obtained from the relative method with those estimated by the single method. The daily averaged receiver DCBs obtained from the two different approaches showed good agreement for 7 days. The root mean square (RMS) value of those differences is 0.83 nanoseconds (ns). The standard deviation of the receiver DCBs estimated by the relative method was smaller than that of the single method. From these results, it is clear that the relative method can obtain more stable receiver DCBs compared with the single method over a short-term period. Additionally, the comparison between the receiver DCBs obtained by the Korea Astronomy and Space Science Institute (KASI) and those of the IGS Global Ionosphere Maps (GIM) showed a good agreement at 0.3 ns. As the accuracy of DCB values significantly affects the accuracy of ionospheric total electron content (TEC), more studies are needed to ensure the reliability and stability of the estimated receiver DCBs.

Internal Consistency, Retest Reliability, and their Implications For Personality Scale Validity

PubMed Central

McCrae, Robert R.; Kurtz, John E.; Yamagata, Shinji; Terracciano, Antonio

2010-01-01

We examined data (N = 34,108) on the differential reliability and validity of facet scales from the NEO Inventories. We evaluated the extent to which (a) psychometric properties of facet scales are generalizable across ages, cultures, and methods of measurement; and (b) validity criteria are associated with different forms of reliability. Composite estimates of facet scale stability, heritability, and cross-observer validity were broadly generalizable. Two estimates of retest reliability were independent predictors of the three validity criteria; none of three estimates of internal consistency was. Available evidence suggests the same pattern of results for other personality inventories. Internal consistency of scales can be useful as a check on data quality, but appears to be of limited utility for evaluating the potential validity of developed scales, and it should not be used as a substitute for retest reliability. Further research on the nature and determinants of retest reliability is needed. PMID:20435807

The reliability of the Hendrich Fall Risk Model in a geriatric hospital.

PubMed

Heinze, Cornelia; Halfens, Ruud; Dassen, Theo

2008-12-01

Aims and objectives.  The purpose of this study was to test the interrater reliability of the Hendrich Fall Risk Model, an instrument to identify patients in a hospital setting with a high risk of falling. Background.  Falls are a serious problem in older patients. Valid and reliable fall risk assessment tools are required to identify high-risk patients and to take adequate preventive measures. Methods.  Seventy older patients were independently and simultaneously assessed by six pairs of raters made up of nursing staff members. Consensus estimates were calculated using simple percentage agreement and consistency estimates using Spearman's rho and intra class coefficient. Results.  Percentage agreement ranged from 0.70 to 0.92 between the six pairs of raters. Spearman's rho coefficients were between 0.54 and 0.80 and the intra class coefficients were between 0.46 and 0.92. Conclusions.  Whereas some pairs of raters obtained considerable interobserver agreement and internal consistency, the others did not. Therefore, it is concluded that the Hendrich Fall Risk Model is not a reliable instrument. The use of more unambiguous operationalized items is preferred. Relevance to clinical practice.  In practice, well operationalized fall risk assessment tools are necessary. Observer agreement should always be investigated after introducing a standardized measurement tool. © 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd.

Reliability and Validity Assessment of a Linear Position Transducer

PubMed Central

Garnacho-Castaño, Manuel V.; López-Lastra, Silvia; Maté-Muñoz, José L.

2015-01-01

The objectives of the study were to determine the validity and reliability of peak velocity (PV), average velocity (AV), peak power (PP) and average power (AP) measurements were made using a linear position transducer. Validity was assessed by comparing measurements simultaneously obtained using the Tendo Weightlifting Analyzer Systemi and T-Force Dynamic Measurement Systemr (Ergotech, Murcia, Spain) during two resistance exercises, bench press (BP) and full back squat (BS), performed by 71 trained male subjects. For the reliability study, a further 32 men completed both lifts using the Tendo Weightlifting Analyzer Systemz in two identical testing sessions one week apart (session 1 vs. session 2). Intraclass correlation coefficients (ICCs) indicating the validity of the Tendo Weightlifting Analyzer Systemi were high, with values ranging from 0.853 to 0.989. Systematic biases and random errors were low to moderate for almost all variables, being higher in the case of PP (bias ±157.56 W; error ±131.84 W). Proportional biases were identified for almost all variables. Test-retest reliability was strong with ICCs ranging from 0.922 to 0.988. Reliability results also showed minimal systematic biases and random errors, which were only significant for PP (bias -19.19 W; error ±67.57 W). Only PV recorded in the BS showed no significant proportional bias. The Tendo Weightlifting Analyzer Systemi emerged as a reliable system for measuring movement velocity and estimating power in resistance exercises. The low biases and random errors observed here (mainly AV, AP) make this device a useful tool for monitoring resistance training. Key points This study determined the validity and reliability of peak velocity, average velocity, peak power and average power measurements made using a linear position transducer The Tendo Weight-lifting Analyzer Systemi emerged as a reliable system for measuring movement velocity and power. PMID:25729300

Theoretical basis, application, reliability, and sample size estimates of a Meridian Energy Analysis Device for Traditional Chinese Medicine Research.

PubMed

Tsai, Ming-Yen; Chen, Shih-Yu; Lin, Chung-Chun

2017-04-01

The Meridian Energy Analysis Device is currently a popular tool in the scientific research of meridian electrophysiology. In this field, it is generally believed that measuring the electrical conductivity of meridians provides information about the balance of bioenergy or Qi-blood in the body. PubMed database based on some original articles from 1956 to 2014 and the authoŕs clinical experience. In this short communication, we provide clinical examples of Meridian Energy Analysis Device application, especially in the field of traditional Chinese medicine, discuss the reliability of the measurements, and put the values obtained into context by considering items of considerable variability and by estimating sample size. The Meridian Energy Analysis Device is making a valuable contribution to the diagnosis of Qi-blood dysfunction. It can be assessed from short-term and long-term meridian bioenergy recordings. It is one of the few methods that allow outpatient traditional Chinese medicine diagnosis, monitoring the progress, therapeutic effect and evaluation of patient prognosis. The holistic approaches underlying the practice of traditional Chinese medicine and new trends in modern medicine toward the use of objective instruments require in-depth knowledge of the mechanisms of meridian energy, and the Meridian Energy Analysis Device can feasibly be used for understanding and interpreting traditional Chinese medicine theory, especially in view of its expansion in Western countries.

The reliability of a quality appraisal tool for studies of diagnostic reliability (QAREL).

PubMed

Lucas, Nicholas; Macaskill, Petra; Irwig, Les; Moran, Robert; Rickards, Luke; Turner, Robin; Bogduk, Nikolai

2013-09-09

The aim of this project was to investigate the reliability of a new 11-item quality appraisal tool for studies of diagnostic reliability (QAREL). The tool was tested on studies reporting the reliability of any physical examination procedure. The reliability of physical examination is a challenging area to study given the complex testing procedures, the range of tests, and lack of procedural standardisation. Three reviewers used QAREL to independently rate 29 articles, comprising 30 studies, published during 2007. The articles were identified from a search of relevant databases using the following string: "Reproducibility of results (MeSH) OR reliability (t.w.) AND Physical examination (MeSH) OR physical examination (t.w.)." A total of 415 articles were retrieved and screened for inclusion. The reviewers undertook an independent trial assessment prior to data collection, followed by a general discussion about how to score each item. At no time did the reviewers discuss individual papers. Reliability was assessed for each item using multi-rater kappa (κ). Multi-rater reliability estimates ranged from κ = 0.27 to 0.92 across all items. Six items were recorded with good reliability (κ > 0.60), three with moderate reliability (κ = 0.41 - 0.60), and two with fair reliability (κ = 0.21 - 0.40). Raters found it difficult to agree about the spectrum of patients included in a study (Item 1) and the correct application and interpretation of the test (Item 10). In this study, we found that QAREL was a reliable assessment tool for studies of diagnostic reliability when raters agreed upon criteria for the interpretation of each item. Nine out of 11 items had good or moderate reliability, and two items achieved fair reliability. The heterogeneity in the tests included in this study may have resulted in an underestimation of the reliability of these two items. We discuss these and other factors that could affect our results and make recommendations for the use of QAREL.

Estimating liver cancer deaths in Thailand based on verbal autopsy study.

PubMed

Waeto, Salwa; Pipatjaturon, Nattakit; Tongkumchum, Phattrawan; Choonpradub, Chamnein; Saelim, Rattikan; Makaje, Nifatamah

2014-01-01

Liver cancer mortality is high in Thailand but utility of related vital statistics is limited due to national vital registration (VR) data being under reported for specific causes of deaths. Accurate methodologies and reliable supplementary data are needed to provide worthy national vital statistics. This study aimed to model liver cancer deaths based on verbal autopsy (VA) study in 2005 to provide more accurate estimates of liver cancer deaths than those reported. The results were used to estimate number of liver cancer deaths during 2000-2009. A verbal autopsy (VA) was carried out in 2005 based on a sample of 9,644 deaths from nine provinces and it provided reliable information on causes of deaths by gender, age group, location of deaths in or outside hospital, and causes of deaths of the VR database. Logistic regression was used to model liver cancer deaths and other variables. The estimated probabilities from the model were applied to liver cancer deaths in the VR database, 2000-2009. Thus, the more accurately VA-estimated numbers of liver cancer deaths were obtained. The model fits the data quite well with sensitivity 0.64. The confidence intervals from statistical model provide the estimates and their precisions. The VA-estimated numbers of liver cancer deaths were higher than the corresponding VR database with inflation factors 1.56 for males and 1.64 for females. The statistical methods used in this study can be applied to available mortality data in developing countries where their national vital registration data are of low quality and supplementary reliable data are available.

Determinants of the reliability of ultrasound tomography sound speed estimates as a surrogate for volumetric breast density

PubMed Central

Khodr, Zeina G.; Sak, Mark A.; Pfeiffer, Ruth M.; Duric, Nebojsa; Littrup, Peter; Bey-Knight, Lisa; Ali, Haythem; Vallieres, Patricia; Sherman, Mark E.; Gierach, Gretchen L.

2015-01-01

Purpose: High breast density, as measured by mammography, is associated with increased breast cancer risk, but standard methods of assessment have limitations including 2D representation of breast tissue, distortion due to breast compression, and use of ionizing radiation. Ultrasound tomography (UST) is a novel imaging method that averts these limitations and uses sound speed measures rather than x-ray imaging to estimate breast density. The authors evaluated the reproducibility of measures of speed of sound and changes in this parameter using UST. Methods: One experienced and five newly trained raters measured sound speed in serial UST scans for 22 women (two scans per person) to assess inter-rater reliability. Intrarater reliability was assessed for four raters. A random effects model was used to calculate the percent variation in sound speed and change in sound speed attributable to subject, scan, rater, and repeat reads. The authors estimated the intraclass correlation coefficients (ICCs) for these measures based on data from the authors’ experienced rater. Results: Median (range) time between baseline and follow-up UST scans was five (1–13) months. Contributions of factors to sound speed variance were differences between subjects (86.0%), baseline versus follow-up scans (7.5%), inter-rater evaluations (1.1%), and intrarater reproducibility (∼0%). When evaluating change in sound speed between scans, 2.7% and ∼0% of variation were attributed to inter- and intrarater variation, respectively. For the experienced rater’s repeat reads, agreement for sound speed was excellent (ICC = 93.4%) and for change in sound speed substantial (ICC = 70.4%), indicating very good reproducibility of these measures. Conclusions: UST provided highly reproducible sound speed measurements, which reflect breast density, suggesting that UST has utility in sensitively assessing change in density. PMID:26429241

Determinants of the reliability of ultrasound tomography sound speed estimates as a surrogate for volumetric breast density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khodr, Zeina G.; Pfeiffer, Ruth M.; Gierach, Gretchen L., E-mail: GierachG@mail.nih.gov

Purpose: High breast density, as measured by mammography, is associated with increased breast cancer risk, but standard methods of assessment have limitations including 2D representation of breast tissue, distortion due to breast compression, and use of ionizing radiation. Ultrasound tomography (UST) is a novel imaging method that averts these limitations and uses sound speed measures rather than x-ray imaging to estimate breast density. The authors evaluated the reproducibility of measures of speed of sound and changes in this parameter using UST. Methods: One experienced and five newly trained raters measured sound speed in serial UST scans for 22 women (twomore » scans per person) to assess inter-rater reliability. Intrarater reliability was assessed for four raters. A random effects model was used to calculate the percent variation in sound speed and change in sound speed attributable to subject, scan, rater, and repeat reads. The authors estimated the intraclass correlation coefficients (ICCs) for these measures based on data from the authors’ experienced rater. Results: Median (range) time between baseline and follow-up UST scans was five (1–13) months. Contributions of factors to sound speed variance were differences between subjects (86.0%), baseline versus follow-up scans (7.5%), inter-rater evaluations (1.1%), and intrarater reproducibility (∼0%). When evaluating change in sound speed between scans, 2.7% and ∼0% of variation were attributed to inter- and intrarater variation, respectively. For the experienced rater’s repeat reads, agreement for sound speed was excellent (ICC = 93.4%) and for change in sound speed substantial (ICC = 70.4%), indicating very good reproducibility of these measures. Conclusions: UST provided highly reproducible sound speed measurements, which reflect breast density, suggesting that UST has utility in sensitively assessing change in density.« less

Psychometrics Matter in Health Behavior: A Long-term Reliability Generalization Study.

PubMed

Pickett, Andrew C; Valdez, Danny; Barry, Adam E

2017-09-01

Despite numerous calls for increased understanding and reporting of reliability estimates, social science research, including the field of health behavior, has been slow to respond and adopt such practices. Therefore, we offer a brief overview of reliability and common reporting errors; we then perform analyses to examine and demonstrate the variability of reliability estimates by sample and over time. Using meta-analytic reliability generalization, we examined the variability of coefficient alpha scores for a well-designed, consistent, nationwide health study, covering a span of nearly 40 years. For each year and sample, reliability varied. Furthermore, reliability was predicted by a sample characteristic that differed among age groups within each administration. We demonstrated that reliability is influenced by the methods and individuals from which a given sample is drawn. Our work echoes previous calls that psychometric properties, particularly reliability of scores, are important and must be considered and reported before drawing statistical conclusions.

Human decomposition and the reliability of a 'Universal' model for post mortem interval estimations.

PubMed

Cockle, Diane L; Bell, Lynne S

2015-08-01

Human decomposition is a complex biological process driven by an array of variables which are not clearly understood. The medico-legal community have long been searching for a reliable method to establish the post-mortem interval (PMI) for those whose deaths have either been hidden, or gone un-noticed. To date, attempts to develop a PMI estimation method based on the state of the body either at the scene or at autopsy have been unsuccessful. One recent study has proposed that two simple formulae, based on the level of decomposition humidity and temperature, could be used to accurately calculate the PMI for bodies outside, on or under the surface worldwide. This study attempted to validate 'Formula I' [1] (for bodies on the surface) using 42 Canadian cases with known PMIs. The results indicated that bodies exposed to warm temperatures consistently overestimated the known PMI by a large and inconsistent margin for Formula I estimations. And for bodies exposed to cold and freezing temperatures (less than 4°C), then the PMI was dramatically under estimated. The ability of 'Formulae II' to estimate the PMI for buried bodies was also examined using a set of 22 known Canadian burial cases. As these cases used in this study are retrospective, some of the data needed for Formula II was not available. The 4.6 value used in Formula II to represent the standard ratio of time that burial decelerates the rate of decomposition was examined. The average time taken to achieve each stage of decomposition both on, and under the surface was compared for the 118 known cases. It was found that the rate of decomposition was not consistent throughout all stages of decomposition. The rates of autolysis above and below the ground were equivalent with the buried cases staying in a state of putrefaction for a prolonged period of time. It is suggested that differences in temperature extremes and humidity levels between geographic regions may make it impractical to apply formulas developed in

Development of reliable pavement models.

DOT National Transportation Integrated Search

2011-05-01

The current report proposes a framework for estimating the reliability of a given pavement structure as analyzed by : the Mechanistic-Empirical Pavement Design Guide (MEPDG). The methodology proposes using a previously fit : response surface, in plac...

Fitting power-laws in empirical data with estimators that work for all exponents

PubMed Central

Hanel, Rudolf; Corominas-Murtra, Bernat; Liu, Bo; Thurner, Stefan

2017-01-01

Most standard methods based on maximum likelihood (ML) estimates of power-law exponents can only be reliably used to identify exponents smaller than minus one. The argument that power laws are otherwise not normalizable, depends on the underlying sample space the data is drawn from, and is true only for sample spaces that are unbounded from above. Power-laws obtained from bounded sample spaces (as is the case for practically all data related problems) are always free of such limitations and maximum likelihood estimates can be obtained for arbitrary powers without restrictions. Here we first derive the appropriate ML estimator for arbitrary exponents of power-law distributions on bounded discrete sample spaces. We then show that an almost identical estimator also works perfectly for continuous data. We implemented this ML estimator and discuss its performance with previous attempts. We present a general recipe of how to use these estimators and present the associated computer codes. PMID:28245249

Report: Eleven Years After Agreement, EPA Has Not Developed Reliable Emission Estimation Methods to Determine Whether Animal Feeding Operations Comply With Clean Air Act and Other Statutes

EPA Pesticide Factsheets

Report #17-P-0396, September 19, 2017. Until the EPA develops sound methods to estimate emissions, the agency cannot reliably determine whether animal feeding operations comply with applicable Clean Air Act requirements.

Prediction of Software Reliability using Bio Inspired Soft Computing Techniques.

PubMed

Diwaker, Chander; Tomar, Pradeep; Poonia, Ramesh C; Singh, Vijander

2018-04-10

A lot of models have been made for predicting software reliability. The reliability models are restricted to using particular types of methodologies and restricted number of parameters. There are a number of techniques and methodologies that may be used for reliability prediction. There is need to focus on parameters consideration while estimating reliability. The reliability of a system may increase or decreases depending on the selection of different parameters used. Thus there is need to identify factors that heavily affecting the reliability of the system. In present days, reusability is mostly used in the various area of research. Reusability is the basis of Component-Based System (CBS). The cost, time and human skill can be saved using Component-Based Software Engineering (CBSE) concepts. CBSE metrics may be used to assess those techniques which are more suitable for estimating system reliability. Soft computing is used for small as well as large-scale problems where it is difficult to find accurate results due to uncertainty or randomness. Several possibilities are available to apply soft computing techniques in medicine related problems. Clinical science of medicine using fuzzy-logic, neural network methodology significantly while basic science of medicine using neural-networks-genetic algorithm most frequently and preferably. There is unavoidable interest shown by medical scientists to use the various soft computing methodologies in genetics, physiology, radiology, cardiology and neurology discipline. CBSE boost users to reuse the past and existing software for making new products to provide quality with a saving of time, memory space, and money. This paper focused on assessment of commonly used soft computing technique like Genetic Algorithm (GA), Neural-Network (NN), Fuzzy Logic, Support Vector Machine (SVM), Ant Colony Optimization (ACO), Particle Swarm Optimization (PSO), and Artificial Bee Colony (ABC). This paper presents working of soft computing

Designing Fault-Injection Experiments for the Reliability of Embedded Systems

NASA Technical Reports Server (NTRS)

White, Allan L.

2012-01-01

This paper considers the long-standing problem of conducting fault-injections experiments to establish the ultra-reliability of embedded systems. There have been extensive efforts in fault injection, and this paper offers a partial summary of the efforts, but these previous efforts have focused on realism and efficiency. Fault injections have been used to examine diagnostics and to test algorithms, but the literature does not contain any framework that says how to conduct fault-injection experiments to establish ultra-reliability. A solution to this problem integrates field-data, arguments-from-design, and fault-injection into a seamless whole. The solution in this paper is to derive a model reduction theorem for a class of semi-Markov models suitable for describing ultra-reliable embedded systems. The derivation shows that a tight upper bound on the probability of system failure can be obtained using only the means of system-recovery times, thus reducing the experimental effort to estimating a reasonable number of easily-observed parameters. The paper includes an example of a system subject to both permanent and transient faults. There is a discussion of integrating fault-injection with field-data and arguments-from-design.

Validating genomic reliabilities and gains from phenotypic updates

USDA-ARS?s Scientific Manuscript database

Reliability can be validated from the variance of the difference of earlier and later estimated breeding values as a fraction of the genetic variance. This new method avoids using squared correlations that can be biased downward by selection. Published genomic reliabilities of U.S. young bulls agree...

A Measure for the Reliability of a Rating Scale Based on Longitudinal Clinical Trial Data

ERIC Educational Resources Information Center

Laenen, Annouschka; Alonso, Ariel; Molenberghs, Geert

2007-01-01

A new measure for reliability of a rating scale is introduced, based on the classical definition of reliability, as the ratio of the true score variance and the total variance. Clinical trial data can be employed to estimate the reliability of the scale in use, whenever repeated measurements are taken. The reliability is estimated from the…

No correlation between ultrasound placental grading at 31-34 weeks of gestation and a surrogate estimate of organ function at term obtained by stereological analysis.

PubMed

Yin, T T; Loughna, P; Ong, S S; Padfield, J; Mayhew, T M

2009-08-01

We test the experimental hypothesis that early changes in the ultrasound appearance of the placenta reflect poor or reduced placental function. The sonographic (Grannum) grade of placental maturity was compared to placental function as expressed by the morphometric oxygen diffusive conductance of the villous membrane. Ultrasonography was used to assess the Grannum grade of 32 placentas at 31-34 weeks of gestation. Indications for the scans included a history of previous fetal abnormalities, previous fetal growth problems or suspicion of IUGR. Placentas were classified from grade 0 (most immature) to grade III (most mature). We did not exclude smokers or complicated pregnancies as we aimed to correlate the early appearance of mature placentas with placental function. After delivery, microscopical fields on formalin-fixed, trichrome-stained histological sections of each placenta were obtained by multistage systematic uniform random sampling. Using design-based stereological methods, the exchange surface areas of peripheral (terminal and intermediate) villi and their fetal capillaries and the arithmetic and harmonic mean thicknesses of the villous membrane (maternal surface of villous trophoblast to adluminal surface of vascular endothelium) were estimated. An index of the variability in thickness of this membrane, and an estimate of its oxygen diffusive conductance, were derived secondarily as were estimates of the mean diameters and total lengths of villi and fetal capillaries. Group comparisons were drawn using analysis of variance. We found no significant differences in placental volume or composition or in the dimensions or diffusive conductances of the villous membrane. Subsequent exclusion of smokers did not alter these main findings. Grannum grades at 31-34 weeks of gestation appear not to provide reliable predictors of the functional capacity of the term placenta as expressed by the surrogate measure, morphometric diffusive conductance.

How reliable are satellite precipitation estimates for driving hydrological models: a verification study over the Mediterranean area

NASA Astrophysics Data System (ADS)

Camici, Stefania; Ciabatta, Luca; Massari, Christian; Brocca, Luca

2017-04-01

, TMPA 3B42-RT, CMORPH, PERSIANN and a new soil moisture-derived rainfall datasets obtained through the application of SM2RAIN algorithm (Brocca et al., 2014) to ASCAT (Advanced SCATterometer) soil moisture product are used in the analysis. The performances obtained with SRPs are compared with those obtained by using ground data during the 6-year period from 2010 to 2015. In addition, the performance obtained by an integration of the above mentioned SRPs is also investigated to see whether merged rainfall observations are able to improve flood simulation. Preliminary analysis were also carried out by using the IMERG early run product of GPM mission. The results highlight that SRPs should be used with caution for rainfall-runoff modelling in the Mediterranean region. Bias correction and model recalibration are necessary steps, even though not always sufficient to achieve satisfactory performances. Indeed, some of the products provide unreliable outcomes, mainly in smaller basins (<500 km2) that, however, represent the main target for flood modelling in the Mediterranean area. The better performances are obtained by integrating different SRPs, and particularly by merging TMPA 3B42-RT and SM2RAIN-ASCAT products. The promising results of the integrated product are expected to increase the confidence on the use of SRPs in hydrological modeling, even in challenging areas as the Mediterranean. REFERENCES Brocca, L., Ciabatta, L., Massari, C., Moramarco, T., Hahn, S., Hasenauer, S., Kidd, R., Dorigo, W., Wagner, W., Levizzani, V. (2014). Soil as a natural rain gauge: estimating global rainfall from satellite soil moisture data. Journal of Geophysical Research, 119(9), 5128-5141, doi:10.1002/2014JD021489. Masseroni, D., Cislaghi, A., Camici, S., Massari, C., Brocca, L. (2017). A reliable rainfall-runoff model for flood forecasting: review and application to a semiurbanized watershed at high flood risk in Italy. Hydrology Research, in press, doi:10.2166/nh.2016.037.

Estimating the Reliability of Electronic Parts in High Radiation Fields

NASA Technical Reports Server (NTRS)

Everline, Chester; Clark, Karla; Man, Guy; Rasmussen, Robert; Johnston, Allan; Kohlhase, Charles; Paulos, Todd

2008-01-01

Radiation effects on materials and electronic parts constrain the lifetime of flight systems visiting Europa. Understanding mission lifetime limits is critical to the design and planning of such a mission. Therefore, the operational aspects of radiation dose are a mission success issue. To predict and manage mission lifetime in a high radiation environment, system engineers need capable tools to trade radiation design choices against system design and reliability, and science achievements. Conventional tools and approaches provided past missions with conservative designs without the ability to predict their lifetime beyond the baseline mission.This paper describes a more systematic approach to understanding spacecraft design margin, allowing better prediction of spacecraft lifetime. This is possible because of newly available electronic parts radiation effects statistics and an enhanced spacecraft system reliability methodology. This new approach can be used in conjunction with traditional approaches for mission design. This paper describes the fundamentals of the new methodology.

LC-MS/MS-based approach for obtaining exposure estimates of metabolites in early clinical trials using radioactive metabolites as reference standards.

PubMed

Zhang, Donglu; Raghavan, Nirmala; Chando, Theodore; Gambardella, Janice; Fu, Yunlin; Zhang, Duxi; Unger, Steve E; Humphreys, W Griffith

2007-12-01

An LC-MS/MS-based approach that employs authentic radioactive metabolites as reference standards was developed to estimate metabolite exposures in early drug development studies. This method is useful to estimate metabolite levels in studies done with non-radiolabeled compounds where metabolite standards are not available to allow standard LC-MS/MS assay development. A metabolite mixture obtained from an in vivo source treated with a radiolabeled compound was partially purified, quantified, and spiked into human plasma to provide metabolite standard curves. Metabolites were analyzed by LC-MS/MS using the specific mass transitions and an internal standard. The metabolite concentrations determined by this approach were found to be comparable to those determined by valid LC-MS/MS assays. This approach does not requires synthesis of authentic metabolites or the knowledge of exact structures of metabolites, and therefore should provide a useful method to obtain early estimates of circulating metabolites in early clinical or toxicological studies.

APPLICATION OF TRAVEL TIME RELIABILITY FOR PERFORMANCE ORIENTED OPERATIONAL PLANNING OF EXPRESSWAYS

NASA Astrophysics Data System (ADS)

Mehran, Babak; Nakamura, Hideki

Evaluation of impacts of congestion improvement scheme s on travel time reliability is very significant for road authorities since travel time reliability repr esents operational performance of expressway segments. In this paper, a methodology is presented to estimate travel tim e reliability prior to implementation of congestion relief schemes based on travel time variation modeling as a function of demand, capacity, weather conditions and road accident s. For subject expressway segmen ts, traffic conditions are modeled over a whole year considering demand and capacity as random variables. Patterns of demand and capacity are generated for each five minute interval by appl ying Monte-Carlo simulation technique, and accidents are randomly generated based on a model that links acci dent rate to traffic conditions. A whole year analysis is performed by comparing de mand and available capacity for each scenario and queue length is estimated through shockwave analysis for each time in terval. Travel times are estimated from refined speed-flow relationships developed for intercity expressways and buffer time index is estimated consequently as a measure of travel time reliability. For validation, estimated reliability indices are compared with measured values from empirical data, and it is shown that the proposed method is suitable for operational evaluation and planning purposes.

Structural reliability methods: Code development status

NASA Astrophysics Data System (ADS)

Millwater, Harry R.; Thacker, Ben H.; Wu, Y.-T.; Cruse, T. A.

1991-05-01

The Probabilistic Structures Analysis Method (PSAM) program integrates state of the art probabilistic algorithms with structural analysis methods in order to quantify the behavior of Space Shuttle Main Engine structures subject to uncertain loadings, boundary conditions, material parameters, and geometric conditions. An advanced, efficient probabilistic structural analysis software program, NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) was developed as a deliverable. NESSUS contains a number of integrated software components to perform probabilistic analysis of complex structures. A nonlinear finite element module NESSUS/FEM is used to model the structure and obtain structural sensitivities. Some of the capabilities of NESSUS/FEM are shown. A Fast Probability Integration module NESSUS/FPI estimates the probability given the structural sensitivities. A driver module, PFEM, couples the FEM and FPI. NESSUS, version 5.0, addresses component reliability, resistance, and risk.

Structural reliability methods: Code development status

NASA Technical Reports Server (NTRS)

Millwater, Harry R.; Thacker, Ben H.; Wu, Y.-T.; Cruse, T. A.

1991-01-01

The Probabilistic Structures Analysis Method (PSAM) program integrates state of the art probabilistic algorithms with structural analysis methods in order to quantify the behavior of Space Shuttle Main Engine structures subject to uncertain loadings, boundary conditions, material parameters, and geometric conditions. An advanced, efficient probabilistic structural analysis software program, NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) was developed as a deliverable. NESSUS contains a number of integrated software components to perform probabilistic analysis of complex structures. A nonlinear finite element module NESSUS/FEM is used to model the structure and obtain structural sensitivities. Some of the capabilities of NESSUS/FEM are shown. A Fast Probability Integration module NESSUS/FPI estimates the probability given the structural sensitivities. A driver module, PFEM, couples the FEM and FPI. NESSUS, version 5.0, addresses component reliability, resistance, and risk.

78 FR 73424 - Retirement of Requirements in Reliability Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-06

... predicated on the view that many violations of requirements currently included in Reliability Standards pose... for Bulk-Power System reliability or may be redundant. The Commission is interested in obtaining views... redundant. The Commission is interested in obtaining views on whether such requirements could be removed...

Binding free energy predictions of farnesoid X receptor (FXR) agonists using a linear interaction energy (LIE) approach with reliability estimation: application to the D3R Grand Challenge 2

NASA Astrophysics Data System (ADS)

Rifai, Eko Aditya; van Dijk, Marc; Vermeulen, Nico P. E.; Geerke, Daan P.

2018-01-01

Computational protein binding affinity prediction can play an important role in drug research but performing efficient and accurate binding free energy calculations is still challenging. In the context of phase 2 of the Drug Design Data Resource (D3R) Grand Challenge 2 we used our automated eTOX ALLIES approach to apply the (iterative) linear interaction energy (LIE) method and we evaluated its performance in predicting binding affinities for farnesoid X receptor (FXR) agonists. Efficiency was obtained by our pre-calibrated LIE models and molecular dynamics (MD) simulations at the nanosecond scale, while predictive accuracy was obtained for a small subset of compounds. Using our recently introduced reliability estimation metrics, we could classify predictions with higher confidence by featuring an applicability domain (AD) analysis in combination with protein-ligand interaction profiling. The outcomes of and agreement between our AD and interaction-profile analyses to distinguish and rationalize the performance of our predictions highlighted the relevance of sufficiently exploring protein-ligand interactions during training and it demonstrated the possibility to quantitatively and efficiently evaluate if this is achieved by using simulation data only.

Beyond alpha: an empirical examination of the effects of different sources of measurement error on reliability estimates for measures of individual differences constructs.

PubMed

Schmidt, Frank L; Le, Huy; Ilies, Remus

2003-06-01

On the basis of an empirical study of measures of constructs from the cognitive domain, the personality domain, and the domain of affective traits, the authors of this study examine the implications of transient measurement error for the measurement of frequently studied individual differences variables. The authors clarify relevant reliability concepts as they relate to transient error and present a procedure for estimating the coefficient of equivalence and stability (L. J. Cronbach, 1947), the only classical reliability coefficient that assesses all 3 major sources of measurement error (random response, transient, and specific factor errors). The authors conclude that transient error exists in all 3 trait domains and is especially large in the domain of affective traits. Their findings indicate that the nearly universal use of the coefficient of equivalence (Cronbach's alpha; L. J. Cronbach, 1951), which fails to assess transient error, leads to overestimates of reliability and undercorrections for biases due to measurement error.

Reliability and validity of the McDonald Play Inventory.

PubMed

McDonald, Ann E; Vigen, Cheryl

2012-01-01

This study examined the ability of a two-part self-report instrument, the McDonald Play Inventory, to reliably and validly measure the play activities and play styles of 7- to 11-yr-old children and to discriminate between the play of neurotypical children and children with known learning and developmental disabilities. A total of 124 children ages 7-11 recruited from a sample of convenience and a subsample of 17 parents participated in this study. Reliability estimates yielded moderate correlations for internal consistency, total test intercorrelations, and test-retest reliability. Validity estimates were established for content and construct validity. The results suggest that a self-report instrument yields reliable and valid measures of a child's perceived play performance and discriminates between the play of children with and without disabilities. Copyright © 2012 by the American Occupational Therapy Association, Inc.

Probability techniques for reliability analysis of composite materials

NASA Technical Reports Server (NTRS)

Wetherhold, Robert C.; Ucci, Anthony M.

1994-01-01

Traditional design approaches for composite materials have employed deterministic criteria for failure analysis. New approaches are required to predict the reliability of composite structures since strengths and stresses may be random variables. This report will examine and compare methods used to evaluate the reliability of composite laminae. The two types of methods that will be evaluated are fast probability integration (FPI) methods and Monte Carlo methods. In these methods, reliability is formulated as the probability that an explicit function of random variables is less than a given constant. Using failure criteria developed for composite materials, a function of design variables can be generated which defines a 'failure surface' in probability space. A number of methods are available to evaluate the integration over the probability space bounded by this surface; this integration delivers the required reliability. The methods which will be evaluated are: the first order, second moment FPI methods; second order, second moment FPI methods; the simple Monte Carlo; and an advanced Monte Carlo technique which utilizes importance sampling. The methods are compared for accuracy, efficiency, and for the conservativism of the reliability estimation. The methodology involved in determining the sensitivity of the reliability estimate to the design variables (strength distributions) and importance factors is also presented.

Predictors of validity and reliability of a physical activity record in adolescents

PubMed Central

2013-01-01

Background Poor to moderate validity of self-reported physical activity instruments is commonly observed in young people in low- and middle-income countries. However, the reasons for such low validity have not been examined in detail. We tested the validity of a self-administered daily physical activity record in adolescents and assessed if personal characteristics or the convenience level of reporting physical activity modified the validity estimates. Methods The study comprised a total of 302 adolescents from an urban and rural area in Ecuador. Validity was evaluated by comparing the record with accelerometer recordings for seven consecutive days. Test-retest reliability was examined by comparing registrations from two records administered three weeks apart. Time spent on sedentary (SED), low (LPA), moderate (MPA) and vigorous (VPA) intensity physical activity was estimated. Bland Altman plots were used to evaluate measurement agreement. We assessed if age, sex, urban or rural setting, anthropometry and convenience of completing the record explained differences in validity estimates using a linear mixed model. Results Although the record provided higher estimates for SED and VPA and lower estimates for LPA and MPA compared to the accelerometer, it showed an overall fair measurement agreement for validity. There was modest reliability for assessing physical activity in each intensity level. Validity was associated with adolescents’ personal characteristics: sex (SED: P = 0.007; LPA: P = 0.001; VPA: P = 0.009) and setting (LPA: P = 0.000; MPA: P = 0.047). Reliability was associated with the convenience of completing the physical activity record for LPA (low convenience: P = 0.014; high convenience: P = 0.045). Conclusions The physical activity record provided acceptable estimates for reliability and validity on a group level. Sex and setting were associated with validity estimates, whereas convenience to fill out the record was

Evaluation of Validity and Reliability for Hierarchical Scales Using Latent Variable Modeling

ERIC Educational Resources Information Center

Raykov, Tenko; Marcoulides, George A.

2012-01-01

A latent variable modeling method is outlined, which accomplishes estimation of criterion validity and reliability for a multicomponent measuring instrument with hierarchical structure. The approach provides point and interval estimates for the scale criterion validity and reliability coefficients, and can also be used for testing composite or…

Constraining uncertainties in water supply reliability in a tropical data scarce basin

NASA Astrophysics Data System (ADS)

Kaune, Alexander; Werner, Micha; Rodriguez, Erasmo; de Fraiture, Charlotte

2015-04-01

Assessing the water supply reliability in river basins is essential for adequate planning and development of irrigated agriculture and urban water systems. In many cases hydrological models are applied to determine the surface water availability in river basins. However, surface water availability and variability is often not appropriately quantified due to epistemic uncertainties, leading to water supply insecurity. The objective of this research is to determine the water supply reliability in order to support planning and development of irrigated agriculture in a tropical, data scarce environment. The approach proposed uses a simple hydrological model, but explicitly includes model parameter uncertainty. A transboundary river basin in the tropical region of Colombia and Venezuela with an approximately area of 2100 km² was selected as a case study. The Budyko hydrological framework was extended to consider climatological input variability and model parameter uncertainty, and through this the surface water reliability to satisfy the irrigation and urban demand was estimated. This provides a spatial estimate of the water supply reliability across the basin. For the middle basin the reliability was found to be less than 30% for most of the months when the water is extracted from an upstream source. Conversely, the monthly water supply reliability was high (r>98%) in the lower basin irrigation areas when water was withdrawn from a source located further downstream. Including model parameter uncertainty provides a complete estimate of the water supply reliability, but that estimate is influenced by the uncertainty in the model. Reducing the uncertainty in the model through improved data and perhaps improved model structure will improve the estimate of the water supply reliability allowing better planning of irrigated agriculture and dependable water allocation decisions.

Methods for estimating missing human skeletal element osteometric dimensions employed in the revised fully technique for estimating stature.

PubMed

Auerbach, Benjamin M

2011-05-01

One of the greatest limitations to the application of the revised Fully anatomical stature estimation method is the inability to measure some of the skeletal elements required in its calculation. These element dimensions cannot be obtained due to taphonomic factors, incomplete excavation, or disease processes, and result in missing data. This study examines methods of imputing these missing dimensions using observable Fully measurements from the skeleton and the accuracy of incorporating these missing element estimations into anatomical stature reconstruction. These are further assessed against stature estimations obtained from mathematical regression formulae for the lower limb bones (femur and tibia). Two thousand seven hundred and seventeen North and South American indigenous skeletons were measured, and subsets of these with observable Fully dimensions were used to simulate missing elements and create estimation methods and equations. Comparisons were made directly between anatomically reconstructed statures and mathematically derived statures, as well as with anatomically derived statures with imputed missing dimensions. These analyses demonstrate that, while mathematical stature estimations are more accurate, anatomical statures incorporating missing dimensions are not appreciably less accurate and are more precise. The anatomical stature estimation method using imputed missing dimensions is supported. Missing element estimation, however, is limited to the vertebral column (only when lumbar vertebrae are present) and to talocalcaneal height (only when femora and tibiae are present). Crania, entire vertebral columns, and femoral or tibial lengths cannot be reliably estimated. Further discussion of the applicability of these methods is discussed. Copyright © 2011 Wiley-Liss, Inc.

Obtaining Parts

Science.gov Websites

The Cosmic Connection Parts for the Berkeley Detector Suppliers: Scintillator Eljen Technology 1 obtain the components needed to build the Berkeley Detector. These companies have helped previous the last update. He estimates that the cost to build a detector varies from $1500 to $2700 depending

Reliability-Based Control Design for Uncertain Systems

NASA Technical Reports Server (NTRS)

Crespo, Luis G.; Kenny, Sean P.

2005-01-01

This paper presents a robust control design methodology for systems with probabilistic parametric uncertainty. Control design is carried out by solving a reliability-based multi-objective optimization problem where the probability of violating design requirements is minimized. Simultaneously, failure domains are optimally enlarged to enable global improvements in the closed-loop performance. To enable an efficient numerical implementation, a hybrid approach for estimating reliability metrics is developed. This approach, which integrates deterministic sampling and asymptotic approximations, greatly reduces the numerical burden associated with complex probabilistic computations without compromising the accuracy of the results. Examples using output-feedback and full-state feedback with state estimation are used to demonstrate the ideas proposed.

An experiment in software reliability

NASA Technical Reports Server (NTRS)

Dunham, J. R.; Pierce, J. L.

1986-01-01

The results of a software reliability experiment conducted in a controlled laboratory setting are reported. The experiment was undertaken to gather data on software failures and is one in a series of experiments being pursued by the Fault Tolerant Systems Branch of NASA Langley Research Center to find a means of credibly performing reliability evaluations of flight control software. The experiment tests a small sample of implementations of radar tracking software having ultra-reliability requirements and uses n-version programming for error detection, and repetitive run modeling for failure and fault rate estimation. The experiment results agree with those of Nagel and Skrivan in that the program error rates suggest an approximate log-linear pattern and the individual faults occurred with significantly different error rates. Additional analysis of the experimental data raises new questions concerning the phenomenon of interacting faults. This phenomenon may provide one explanation for software reliability decay.

Near surface water content estimation using GPR data: investigations within California vineyards

NASA Astrophysics Data System (ADS)

Hubbard, S.; Grote, K.; Lunt, I.; Rubin, Y.

2003-04-01

Detailed estimates of water content are necessary for variety of hydrogeological investigations. In viticulture applications, this information is particularly useful for assisting the design of both vineyard layout and efficient irrigation/agrochemical application. However, it is difficult to obtain sufficient information about the spatial variation of water content within the root zone using conventional point or wellbore measurements. We have investigated the applicability of ground penetrating radar (GPR) methods to estimate near surface water content within two California vineyard study sites: the Robert Mondavi Vineyard in Napa County and the Dehlinger Vineyard within Sonoma County. Our research at the winery study sites involves assessing the feasibility of obtaining accurate, non-invasive and dense estimates of water content and the changes in water content over space and time using both groundwave and reflected GPR events. We will present the spatial and temporal estimates of water content obtained from the GPR data at both sites. We will compare our estimates with conventional measurements of water content (obtained using gravimetric, TDR, and neutron probe techniques) as well as with soil texture and plant vigor measurements. Through these comparisons, we will illustrate the potential of GPR for providing reliable and spatially dense water content estimates and the linkages between water content, soil properties and ecosystem responses at the two study sites.

Reliability generalization study of the Yale-Brown Obsessive-Compulsive Scale for children and adolescents.

PubMed

López-Pina, José Antonio; Sánchez-Meca, Julio; López-López, José Antonio; Marín-Martínez, Fulgencio; Núñez-Núñez, Rosa Ma; Rosa-Alcázar, Ana I; Gómez-Conesa, Antonia; Ferrer-Requena, Josefa

2015-01-01

The Yale-Brown Obsessive-Compulsive Scale for children and adolescents (CY-BOCS) is a frequently applied test to assess obsessive-compulsive symptoms. We conducted a reliability generalization meta-analysis on the CY-BOCS to estimate the average reliability, search for reliability moderators, and propose a predictive model that researchers and clinicians can use to estimate the expected reliability of the CY-BOCS scores. A total of 47 studies reporting a reliability coefficient with the data at hand were included in the meta-analysis. The results showed good reliability and a large variability associated to the standard deviation of total scores and sample size.

The utility of online panel surveys versus computer-assisted interviews in obtaining substance-use prevalence estimates in the Netherlands.

PubMed

Spijkerman, Renske; Knibbe, Ronald; Knoops, Kim; Van De Mheen, Dike; Van Den Eijnden, Regina

2009-10-01

Rather than using the traditional, costly method of personal interviews in a general population sample, substance-use prevalence rates can be derived more conveniently from data collected among members of an online access panel. To examine the utility of this method, we compared the outcomes of an online survey with those obtained with the computer-assisted personal interviews (CAPI) method. Data were gathered from a large sample of online panellists and in a two-stage stratified sample of the Dutch population using the CAPI method. The Netherlands. Participants  The online sample comprised 57 125 Dutch online panellists (15-64 years) of Survey Sampling International LLC (SSI), and the CAPI cohort 7204 respondents (15-64 years). All participants answered identical questions about their use of alcohol, cannabis, ecstasy, cocaine and performance-enhancing drugs. The CAPI respondents were asked additionally about internet access and online panel membership. Both data sets were weighted statistically according to the distribution of demographic characteristics of the general Dutch population. Response rates were 35.5% (n = 20 282) for the online panel cohort and 62.7% (n = 4516) for the CAPI cohort. The data showed almost consistently lower substance-use prevalence rates for the CAPI respondents. Although the observed differences could be due to bias in both data sets, coverage and non-response bias were higher in the online panel survey. Despite its economic advantage, the online panel survey showed stronger non-response and coverage bias than the CAPI survey, leading to less reliable estimates of substance use in the general population. © 2009 The Authors. Journal compilation © 2009 Society for the Study of Addiction.

Reliability of CKD-EPI predictive equation in estimating chronic kidney disease prevalence in the Croatian endemic nephropathy area.

PubMed

Fuček, Mirjana; Dika, Živka; Karanović, Sandra; Vuković Brinar, Ivana; Premužić, Vedran; Kos, Jelena; Cvitković, Ante; Mišić, Maja; Samardžić, Josip; Rogić, Dunja; Jelaković, Bojan

2018-02-15

Chronic kidney disease (CKD) is a significant public health problem and it is not possible to precisely predict its progression to terminal renal failure. According to current guidelines, CKD stages are classified based on the estimated glomerular filtration rate (eGFR) and albuminuria. Aims of this study were to determine the reliability of predictive equation in estimation of CKD prevalence in Croatian areas with endemic nephropathy (EN), compare the results with non-endemic areas, and to determine if the prevalence of CKD stages 3-5 was increased in subjects with EN. A total of 1573 inhabitants of the Croatian Posavina rural area from 6 endemic and 3 non-endemic villages were enrolled. Participants were classified according to the modified criteria of the World Health Organization for EN. Estimated GFR was calculated using Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI). The results showed a very high CKD prevalence in the Croatian rural area (19%). CKD prevalence was significantly higher in EN then in non EN villages with the lowest eGFR value in diseased subgroup. eGFR correlated significantly with the diagnosis of EN. Kidney function assessment using CKD-EPI predictive equation proved to be a good marker in differentiating the study subgroups, remained as one of the diagnostic criteria for EN.

A Bayesian approach to reliability and confidence

NASA Technical Reports Server (NTRS)

Barnes, Ron

1989-01-01

The historical evolution of NASA's interest in quantitative measures of reliability assessment is outlined. The introduction of some quantitative methodologies into the Vehicle Reliability Branch of the Safety, Reliability and Quality Assurance (SR and QA) Division at Johnson Space Center (JSC) was noted along with the development of the Extended Orbiter Duration--Weakest Link study which will utilize quantitative tools for a Bayesian statistical analysis. Extending the earlier work of NASA sponsor, Richard Heydorn, researchers were able to produce a consistent Bayesian estimate for the reliability of a component and hence by a simple extension for a system of components in some cases where the rate of failure is not constant but varies over time. Mechanical systems in general have this property since the reliability usually decreases markedly as the parts degrade over time. While they have been able to reduce the Bayesian estimator to a simple closed form for a large class of such systems, the form for the most general case needs to be attacked by the computer. Once a table is generated for this form, researchers will have a numerical form for the general solution. With this, the corresponding probability statements about the reliability of a system can be made in the most general setting. Note that the utilization of uniform Bayesian priors represents a worst case scenario in the sense that as researchers incorporate more expert opinion into the model, they will be able to improve the strength of the probability calculations.

Comparability and Reliability Considerations of Adequate Yearly Progress

ERIC Educational Resources Information Center

Maier, Kimberly S.; Maiti, Tapabrata; Dass, Sarat C.; Lim, Chae Young

2012-01-01

The purpose of this study is to develop an estimate of Adequate Yearly Progress (AYP) that will allow for reliable and valid comparisons among student subgroups, schools, and districts. A shrinkage-type estimator of AYP using the Bayesian framework is described. Using simulated data, the performance of the Bayes estimator will be compared to…

Validating the absolute reliability of a fat free mass estimate equation in hemodialysis patients using near-infrared spectroscopy.

PubMed

Kono, Kenichi; Nishida, Yusuke; Moriyama, Yoshihumi; Taoka, Masahiro; Sato, Takashi

2015-06-01

The assessment of nutritional states using fat free mass (FFM) measured with near-infrared spectroscopy (NIRS) is clinically useful. This measurement should incorporate the patient's post-dialysis weight ("dry weight"), in order to exclude the effects of any change in water mass. We therefore used NIRS to investigate the regression, independent variables, and absolute reliability of FFM in dry weight. The study included 47 outpatients from the hemodialysis unit. Body weight was measured before dialysis, and FFM was measured using NIRS before and after dialysis treatment. Multiple regression analysis was used to estimate the FFM in dry weight as the dependent variable. The measured FFM before dialysis treatment (Mw-FFM), and the difference between measured and dry weight (Mw-Dw) were independent variables. We performed Bland-Altman analysis to detect errors between the statistically estimated FFM and the measured FFM after dialysis treatment. The multiple regression equation to estimate the FFM in dry weight was: Dw-FFM = 0.038 + (0.984 × Mw-FFM) + (-0.571 × [Mw-Dw]); R(2)  = 0.99). There was no systematic bias between the estimated and the measured values of FFM in dry weight. Using NIRS, FFM in dry weight can be calculated by an equation including FFM in measured weight and the difference between the measured weight and the dry weight. © 2015 The Authors. Therapeutic Apheresis and Dialysis © 2015 International Society for Apheresis.

Two-dimensional echo-cardiographic estimation of left atrial volume and volume load in patients with congenital heart disease.

PubMed

Kawaguchi, A; Linde, L M; Imachi, T; Mizuno, H; Akutsu, H

1983-12-01

To estimate the left atrial volume (LAV) and pulmonary blood flow in patients with congenital heart disease (CHD), we employed two-dimensional echocardiography (TDE). The LAV was measured in dimensions other than those obtained in conventional M-mode echocardiography (M-mode echo). Mathematical and geometrical models for LAV calculation using the standard long-axis, short-axis and apical four-chamber planes were devised and found to be reliable in a preliminary study using porcine heart preparations, although length (10%), area (20%) and volume (38%) were significantly and consistently underestimated with echocardiography. Those models were then applied and correlated with angiocardiograms (ACG) in 25 consecutive patients with suspected CHD. In terms of the estimation of the absolute LAV, accuracy seemed commensurate with the number of the dimensions measured. The correlation between data obtained by TDE and ACG varied with changing hemodynamics such as cardiac cycle, absolute LAV and presence or absence of volume load. The left atrium was found to become spherical and progressively underestimated with TDE at ventricular endsystole, in larger LAV and with increased volume load. Since this tendency became less pronounced in measuring additional dimensions, reliable estimation of the absolute LAV and volume load was possible when 2 or 3 dimensions were measured. Among those calculation models depending on 2 or 3 dimensional measurements, there was only a small difference in terms of accuracy and predictability, although algorithm used varied from one model to another. This suggests that accurate cross-sectional area measurement is critically important for volume estimation rather than any particular algorithm involved. Cross-sectional area measurement by TDE integrated into a three dimensional equivalent allowed a reliable estimate of the LAV or volume load in a variety of hemodynamic situations where M-mode echo was not reliable.

Estimations of population density for selected periods between the Neolithic and AD 1800.

PubMed

Zimmermann, Andreas; Hilpert, Johanna; Wendt, Karl Peter

2009-04-01

Abstract We describe a combination of methods applied to obtain reliable estimations of population density using archaeological data. The combination is based on a hierarchical model of scale levels. The necessary data and methods used to obtain the results are chosen so as to define transfer functions from one scale level to another. We apply our method to data sets from western Germany that cover early Neolithic, Iron Age, Roman, and Merovingian times as well as historical data from AD 1800. Error margins and natural and historical variability are discussed. Our results for nonstate societies are always lower than conventional estimations compiled from the literature, and we discuss the reasons for this finding. At the end, we compare the calculated local and global population densities with other estimations from different parts of the world.

Obtaining parsimonious hydraulic conductivity fields using head and transport observations: A Bayesian geostatistical parameter estimation approach

NASA Astrophysics Data System (ADS)

Fienen, M.; Hunt, R.; Krabbenhoft, D.; Clemo, T.

2009-08-01

Flow path delineation is a valuable tool for interpreting the subsurface hydrogeochemical environment. Different types of data, such as groundwater flow and transport, inform different aspects of hydrogeologic parameter values (hydraulic conductivity in this case) which, in turn, determine flow paths. This work combines flow and transport information to estimate a unified set of hydrogeologic parameters using the Bayesian geostatistical inverse approach. Parameter flexibility is allowed by using a highly parameterized approach with the level of complexity informed by the data. Despite the effort to adhere to the ideal of minimal a priori structure imposed on the problem, extreme contrasts in parameters can result in the need to censor correlation across hydrostratigraphic bounding surfaces. These partitions segregate parameters into facies associations. With an iterative approach in which partitions are based on inspection of initial estimates, flow path interpretation is progressively refined through the inclusion of more types of data. Head observations, stable oxygen isotopes (18O/16O ratios), and tritium are all used to progressively refine flow path delineation on an isthmus between two lakes in the Trout Lake watershed, northern Wisconsin, United States. Despite allowing significant parameter freedom by estimating many distributed parameter values, a smooth field is obtained.

Obtaining parsimonious hydraulic conductivity fields using head and transport observations: A Bayesian geostatistical parameter estimation approach

USGS Publications Warehouse

Fienen, M.; Hunt, R.; Krabbenhoft, D.; Clemo, T.

2009-01-01

Flow path delineation is a valuable tool for interpreting the subsurface hydrogeochemical environment. Different types of data, such as groundwater flow and transport, inform different aspects of hydrogeologic parameter values (hydraulic conductivity in this case) which, in turn, determine flow paths. This work combines flow and transport information to estimate a unified set of hydrogeologic parameters using the Bayesian geostatistical inverse approach. Parameter flexibility is allowed by using a highly parameterized approach with the level of complexity informed by the data. Despite the effort to adhere to the ideal of minimal a priori structure imposed on the problem, extreme contrasts in parameters can result in the need to censor correlation across hydrostratigraphic bounding surfaces. These partitions segregate parameters into facies associations. With an iterative approach in which partitions are based on inspection of initial estimates, flow path interpretation is progressively refined through the inclusion of more types of data. Head observations, stable oxygen isotopes (18O/16O ratios), and tritium are all used to progressively refine flow path delineation on an isthmus between two lakes in the Trout Lake watershed, northern Wisconsin, United States. Despite allowing significant parameter freedom by estimating many distributed parameter values, a smooth field is obtained.

Direct volume estimation without segmentation

NASA Astrophysics Data System (ADS)

Zhen, X.; Wang, Z.; Islam, A.; Bhaduri, M.; Chan, I.; Li, S.

2015-03-01

Volume estimation plays an important role in clinical diagnosis. For example, cardiac ventricular volumes including left ventricle (LV) and right ventricle (RV) are important clinical indicators of cardiac functions. Accurate and automatic estimation of the ventricular volumes is essential to the assessment of cardiac functions and diagnosis of heart diseases. Conventional methods are dependent on an intermediate segmentation step which is obtained either manually or automatically. However, manual segmentation is extremely time-consuming, subjective and highly non-reproducible; automatic segmentation is still challenging, computationally expensive, and completely unsolved for the RV. Towards accurate and efficient direct volume estimation, our group has been researching on learning based methods without segmentation by leveraging state-of-the-art machine learning techniques. Our direct estimation methods remove the accessional step of segmentation and can naturally deal with various volume estimation tasks. Moreover, they are extremely flexible to be used for volume estimation of either joint bi-ventricles (LV and RV) or individual LV/RV. We comparatively study the performance of direct methods on cardiac ventricular volume estimation by comparing with segmentation based methods. Experimental results show that direct estimation methods provide more accurate estimation of cardiac ventricular volumes than segmentation based methods. This indicates that direct estimation methods not only provide a convenient and mature clinical tool for cardiac volume estimation but also enables diagnosis of cardiac diseases to be conducted in a more efficient and reliable way.

Approximation Model Building for Reliability & Maintainability Characteristics of Reusable Launch Vehicles

NASA Technical Reports Server (NTRS)

Unal, Resit; Morris, W. Douglas; White, Nancy H.; Lepsch, Roger A.; Brown, Richard W.

2000-01-01

This paper describes the development of parametric models for estimating operational reliability and maintainability (R&M) characteristics for reusable vehicle concepts, based on vehicle size and technology support level. A R&M analysis tool (RMAT) and response surface methods are utilized to build parametric approximation models for rapidly estimating operational R&M characteristics such as mission completion reliability. These models that approximate RMAT, can then be utilized for fast analysis of operational requirements, for lifecycle cost estimating and for multidisciplinary sign optimization.

Biopsy Specimens Obtained 7 Days After Starting Chemoradiotherapy (CRT) Provide Reliable Predictors of Response to CRT for Rectal Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Toshiyuki; Sadahiro, Sotaro, E-mail: sadahiro@is.icc.u-tokai.ac.jp; Tanaka, Akira

2013-04-01

Purpose: Preoperative chemoradiation therapy (CRT) significantly decreases local recurrence in locally advanced rectal cancer. Various biomarkers in biopsy specimens obtained before CRT have been proposed as predictors of response. However, reliable biomarkers remain to be established. Methods and Materials: The study group comprised 101 consecutive patients with locally advanced rectal cancer who received preoperative CRT with oral uracil/tegafur (UFT) or S-1. We evaluated histologic findings on hematoxylin and eosin (H and E) staining and immunohistochemical expressions of Ki67, p53, p21, and apoptosis in biopsy specimens obtained before CRT and 7 days after starting CRT. These findings were contrasted with themore » histologic response and the degree of tumor shrinkage. Results: In biopsy specimens obtained before CRT, histologic marked regression according to the Japanese Classification of Colorectal Carcinoma (JCCC) criteria and the degree of tumor shrinkage on barium enema examination (BE) were significantly greater in patients with p21-positive tumors than in those with p21-negative tumors (P=.04 and P<.01, respectively). In biopsy specimens obtained 7 days after starting CRT, pathologic complete response, histologic marked regression according to both the tumor regression criteria and JCCC criteria, and T downstaging were significantly greater in patients with apoptosis-positive and p21-positive tumors than in those with apoptosis-negative (P<.01, P=.02, P=.01, and P<.01, respectively) or p21-negative tumors (P=.03, P<.01, P<.01, and P=.02, respectively). The degree of tumor shrinkage on both BE as well as MRI was significantly greater in patients with apoptosis-positive and with p21-positive tumors than in those with apoptosis-negative or p21-negative tumors, respectively. Histologic changes in H and E-stained biopsy specimens 7 days after starting CRT significantly correlated with pathologic complete response and marked regression on both JCCC and tumor

A method of bias correction for maximal reliability with dichotomous measures.

PubMed

Penev, Spiridon; Raykov, Tenko

2010-02-01

This paper is concerned with the reliability of weighted combinations of a given set of dichotomous measures. Maximal reliability for such measures has been discussed in the past, but the pertinent estimator exhibits a considerable bias and mean squared error for moderate sample sizes. We examine this bias, propose a procedure for bias correction, and develop a more accurate asymptotic confidence interval for the resulting estimator. In most empirically relevant cases, the bias correction and mean squared error correction can be performed simultaneously. We propose an approximate (asymptotic) confidence interval for the maximal reliability coefficient, discuss the implementation of this estimator, and investigate the mean squared error of the associated asymptotic approximation. We illustrate the proposed methods using a numerical example.

Age estimation by amino acid racemization in human teeth.

PubMed

Ohtani, Susumu; Yamamoto, Toshiharu

2010-11-01

When an unidentified body is found, it is essential to establish the personal identity of the body in addition to investigating the cause of death. Identification is one of the most important functions of forensic dentistry. Fingerprint, dental, and DNA analysis can be used to accurately identify a body. However, if no information is available for identification, age estimation can contribute to the resolution of a case. The authors have been using aspartic acid racemization rates in dentin (D-aspartic acid/L-aspartic acid: D/L Asp) as an index for age estimation and have obtained satisfactory results. We report five cases of age estimation using the racemization method. In all five cases, estimated ages were accurate within a range ±3 years. We conclude that the racemization method is a reliable and practical method for estimating age. © 2010 American Academy of Forensic Sciences.

Reliability of drivers in urban intersections.

PubMed

Gstalter, Herbert; Fastenmeier, Wolfgang

2010-01-01

The concept of human reliability has been widely used in industrial settings by human factors experts to optimise the person-task fit. Reliability is estimated by the probability that a task will successfully be completed by personnel in a given stage of system operation. Human Reliability Analysis (HRA) is a technique used to calculate human error probabilities as the ratio of errors committed to the number of opportunities for that error. To transfer this notion to the measurement of car driver reliability the following components are necessary: a taxonomy of driving tasks, a definition of correct behaviour in each of these tasks, a list of errors as deviations from the correct actions and an adequate observation method to register errors and opportunities for these errors. Use of the SAFE-task analysis procedure recently made it possible to derive driver errors directly from the normative analysis of behavioural requirements. Driver reliability estimates could be used to compare groups of tasks (e.g. different types of intersections with their respective regulations) as well as groups of drivers' or individual drivers' aptitudes. This approach was tested in a field study with 62 drivers of different age groups. The subjects drove an instrumented car and had to complete an urban test route, the main features of which were 18 intersections representing six different driving tasks. The subjects were accompanied by two trained observers who recorded driver errors using standardized observation sheets. Results indicate that error indices often vary between both the age group of drivers and the type of driving task. The highest error indices occurred in the non-signalised intersection tasks and the roundabout, which exactly equals the corresponding ratings of task complexity from the SAFE analysis. A comparison of age groups clearly shows the disadvantage of older drivers, whose error indices in nearly all tasks are significantly higher than those of the other groups

Error Estimation for the Linearized Auto-Localization Algorithm

PubMed Central

Guevara, Jorge; Jiménez, Antonio R.; Prieto, Jose Carlos; Seco, Fernando

2012-01-01

The Linearized Auto-Localization (LAL) algorithm estimates the position of beacon nodes in Local Positioning Systems (LPSs), using only the distance measurements to a mobile node whose position is also unknown. The LAL algorithm calculates the inter-beacon distances, used for the estimation of the beacons’ positions, from the linearized trilateration equations. In this paper we propose a method to estimate the propagation of the errors of the inter-beacon distances obtained with the LAL algorithm, based on a first order Taylor approximation of the equations. Since the method depends on such approximation, a confidence parameter τ is defined to measure the reliability of the estimated error. Field evaluations showed that by applying this information to an improved weighted-based auto-localization algorithm (WLAL), the standard deviation of the inter-beacon distances can be improved by more than 30% on average with respect to the original LAL method. PMID:22736965

Extended Importance Sampling for Reliability Analysis under Evidence Theory

NASA Astrophysics Data System (ADS)

Yuan, X. K.; Chen, B.; Zhang, B. Q.

2018-05-01

In early engineering practice, the lack of data and information makes uncertainty difficult to deal with. However, evidence theory has been proposed to handle uncertainty with limited information as an alternative way to traditional probability theory. In this contribution, a simulation-based approach, called ‘Extended importance sampling’, is proposed based on evidence theory to handle problems with epistemic uncertainty. The proposed approach stems from the traditional importance sampling for reliability analysis under probability theory, and is developed to handle the problem with epistemic uncertainty. It first introduces a nominal instrumental probability density function (PDF) for every epistemic uncertainty variable, and thus an ‘equivalent’ reliability problem under probability theory is obtained. Then the samples of these variables are generated in a way of importance sampling. Based on these samples, the plausibility and belief (upper and lower bounds of probability) can be estimated. It is more efficient than direct Monte Carlo simulation. Numerical and engineering examples are given to illustrate the efficiency and feasible of the proposed approach.

The relative impact of baryons and cluster shape on weak lensing mass estimates of galaxy clusters

NASA Astrophysics Data System (ADS)

Lee, B. E.; Le Brun, A. M. C.; Haq, M. E.; Deering, N. J.; King, L. J.; Applegate, D.; McCarthy, I. G.

2018-05-01

Weak gravitational lensing depends on the integrated mass along the line of sight. Baryons contribute to the mass distribution of galaxy clusters and the resulting mass estimates from lensing analysis. We use the cosmo-OWLS suite of hydrodynamic simulations to investigate the impact of baryonic processes on the bias and scatter of weak lensing mass estimates of clusters. These estimates are obtained by fitting NFW profiles to mock data using MCMC techniques. In particular, we examine the difference in estimates between dark matter-only runs and those including various prescriptions for baryonic physics. We find no significant difference in the mass bias when baryonic physics is included, though the overall mass estimates are suppressed when feedback from AGN is included. For lowest-mass systems for which a reliable mass can be obtained (M200 ≈ 2 × 1014M⊙), we find a bias of ≈-10 per cent. The magnitude of the bias tends to decrease for higher mass clusters, consistent with no bias for the most massive clusters which have masses comparable to those found in the CLASH and HFF samples. For the lowest mass clusters, the mass bias is particularly sensitive to the fit radii and the limits placed on the concentration prior, rendering reliable mass estimates difficult. The scatter in mass estimates between the dark matter-only and the various baryonic runs is less than between different projections of individual clusters, highlighting the importance of triaxiality.

Reliability of Summed Item Scores Using Structural Equation Modeling: An Alternative to Coefficient Alpha

ERIC Educational Resources Information Center

Green, Samuel B.; Yang, Yanyun

2009-01-01

A method is presented for estimating reliability using structural equation modeling (SEM) that allows for nonlinearity between factors and item scores. Assuming the focus is on consistency of summed item scores, this method for estimating reliability is preferred to those based on linear SEM models and to the most commonly reported estimate of…

System and Software Reliability (C103)

NASA Technical Reports Server (NTRS)

Wallace, Dolores

2003-01-01

Within the last decade better reliability models (hardware. software, system) than those currently used have been theorized and developed but not implemented in practice. Previous research on software reliability has shown that while some existing software reliability models are practical, they are no accurate enough. New paradigms of development (e.g. OO) have appeared and associated reliability models have been proposed posed but not investigated. Hardware models have been extensively investigated but not integrated into a system framework. System reliability modeling is the weakest of the three. NASA engineers need better methods and tools to demonstrate that the products meet NASA requirements for reliability measurement. For the new models for the software component of the last decade, there is a great need to bring them into a form that they can be used on software intensive systems. The Statistical Modeling and Estimation of Reliability Functions for Systems (SMERFS'3) tool is an existing vehicle that may be used to incorporate these new modeling advances. Adapting some existing software reliability modeling changes to accommodate major changes in software development technology may also show substantial improvement in prediction accuracy. With some additional research, the next step is to identify and investigate system reliability. System reliability models could then be incorporated in a tool such as SMERFS'3. This tool with better models would greatly add value in assess in GSFC projects.

Evaluation of Reliability Coefficients for Two-Level Models via Latent Variable Analysis

ERIC Educational Resources Information Center

Raykov, Tenko; Penev, Spiridon

2010-01-01

A latent variable analysis procedure for evaluation of reliability coefficients for 2-level models is outlined. The method provides point and interval estimates of group means' reliability, overall reliability of means, and conditional reliability. In addition, the approach can be used to test simple hypotheses about these parameters. The…

Experiments in fault tolerant software reliability

NASA Technical Reports Server (NTRS)

Mcallister, David F.; Tai, K. C.; Vouk, Mladen A.

1987-01-01

The reliability of voting was evaluated in a fault-tolerant software system for small output spaces. The effectiveness of the back-to-back testing process was investigated. Version 3.0 of the RSDIMU-ATS, a semi-automated test bed for certification testing of RSDIMU software, was prepared and distributed. Software reliability estimation methods based on non-random sampling are being studied. The investigation of existing fault-tolerance models was continued and formulation of new models was initiated.

Quantifying similarity in reliability surfaces using the probability of agreement

DOE PAGES

Stevens, Nathaniel T.; Anderson-Cook, Christine Michaela

2017-03-30

When separate populations exhibit similar reliability as a function of multiple explanatory variables, combining them into a single population is tempting. This can simplify future predictions and reduce uncertainty associated with estimation. However, combining these populations may introduce bias if the underlying relationships are in fact different. The probability of agreement formally and intuitively quantifies the similarity of estimated reliability surfaces across a two-factor input space. An example from the reliability literature demonstrates the utility of the approach when deciding whether to combine two populations or to keep them as distinct. As a result, new graphical summaries provide strategies formore » visualizing the results.« less

Quantifying similarity in reliability surfaces using the probability of agreement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevens, Nathaniel T.; Anderson-Cook, Christine Michaela

When separate populations exhibit similar reliability as a function of multiple explanatory variables, combining them into a single population is tempting. This can simplify future predictions and reduce uncertainty associated with estimation. However, combining these populations may introduce bias if the underlying relationships are in fact different. The probability of agreement formally and intuitively quantifies the similarity of estimated reliability surfaces across a two-factor input space. An example from the reliability literature demonstrates the utility of the approach when deciding whether to combine two populations or to keep them as distinct. As a result, new graphical summaries provide strategies formore » visualizing the results.« less

Developing Confidence Limits For Reliability Of Software

NASA Technical Reports Server (NTRS)

Hayhurst, Kelly J.

1991-01-01

Technique developed for estimating reliability of software by use of Moranda geometric de-eutrophication model. Pivotal method enables straightforward construction of exact bounds with associated degree of statistical confidence about reliability of software. Confidence limits thus derived provide precise means of assessing quality of software. Limits take into account number of bugs found while testing and effects of sampling variation associated with random order of discovering bugs.

Reliability Generalization of Scores on the Spielberger State-Trait Anxiety Inventory.

ERIC Educational Resources Information Center

Barnes, Laura L. B.; Harp, Diane; Jung, Woo Sik

2002-01-01

Conducted a reliability generalization study for the State-Trait Anxiety Inventory (C. Spielberger, 1983) by reviewing and classifying 816 research articles. Average reliability coefficients were acceptable for both internal consistency and test-retest reliability, but variation was present among the estimates. Other differences are discussed.…

System reliability approaches for advanced propulsion system structures

NASA Technical Reports Server (NTRS)

Cruse, T. A.; Mahadevan, S.

1991-01-01

This paper identifies significant issues that pertain to the estimation and use of system reliability in the design of advanced propulsion system structures. Linkages between the reliabilities of individual components and their effect on system design issues such as performance, cost, availability, and certification are examined. The need for system reliability computation to address the continuum nature of propulsion system structures and synergistic progressive damage modes has been highlighted. Available system reliability models are observed to apply only to discrete systems. Therefore a sequential structural reanalysis procedure is formulated to rigorously compute the conditional dependencies between various failure modes. The method is developed in a manner that supports both top-down and bottom-up analyses in system reliability.

Automated reliability assessment for spectroscopic redshift measurements

NASA Astrophysics Data System (ADS)

Jamal, S.; Le Brun, V.; Le Fèvre, O.; Vibert, D.; Schmitt, A.; Surace, C.; Copin, Y.; Garilli, B.; Moresco, M.; Pozzetti, L.

2018-03-01

Context. Future large-scale surveys, such as the ESA Euclid mission, will produce a large set of galaxy redshifts (≥106) that will require fully automated data-processing pipelines to analyze the data, extract crucial information and ensure that all requirements are met. A fundamental element in these pipelines is to associate to each galaxy redshift measurement a quality, or reliability, estimate. Aim. In this work, we introduce a new approach to automate the spectroscopic redshift reliability assessment based on machine learning (ML) and characteristics of the redshift probability density function. Methods: We propose to rephrase the spectroscopic redshift estimation into a Bayesian framework, in order to incorporate all sources of information and uncertainties related to the redshift estimation process and produce a redshift posterior probability density function (PDF). To automate the assessment of a reliability flag, we exploit key features in the redshift posterior PDF and machine learning algorithms. Results: As a working example, public data from the VIMOS VLT Deep Survey is exploited to present and test this new methodology. We first tried to reproduce the existing reliability flags using supervised classification in order to describe different types of redshift PDFs, but due to the subjective definition of these flags (classification accuracy 58%), we soon opted for a new homogeneous partitioning of the data into distinct clusters via unsupervised classification. After assessing the accuracy of the new clusters via resubstitution and test predictions (classification accuracy 98%), we projected unlabeled data from preliminary mock simulations for the Euclid space mission into this mapping to predict their redshift reliability labels. Conclusions: Through the development of a methodology in which a system can build its own experience to assess the quality of a parameter, we are able to set a preliminary basis of an automated reliability assessment for

Reliability of the Language ENvironment Analysis system (LENA™) in European French.

PubMed

Canault, Mélanie; Le Normand, Marie-Thérèse; Foudil, Samy; Loundon, Natalie; Thai-Van, Hung

2016-09-01

In this study, we examined the accuracy of the Language ENvironment Analysis (LENA) system in European French. LENA is a digital recording device with software that facilitates the collection and analysis of audio recordings from young children, providing automated measures of the speech overheard and produced by the child. Eighteen native French-speaking children, who were divided into six age groups ranging from 3 to 48 months old, were recorded about 10-16 h per day, three days a week. A total of 324 samples (six 10-min chunks of recordings) were selected and then transcribed according to the CHAT format. Simple and mixed linear models between the LENA and human adult word count (AWC) and child vocalization count (CVC) estimates were performed, to determine to what extent the automatic and the human methods agreed. Both the AWC and CVC estimates were very reliable (r = .64 and .71, respectively) for the 324 samples. When controlling the random factors of participants and recordings, 1 h was sufficient to obtain a reliable sample. It was, however, found that two age groups (7-12 months and 13-18 months) had a significant effect on the AWC data and that the second day of recording had a significant effect on the CVC data. When noise-related factors were added to the model, only a significant effect of signal-to-noise ratio was found on the AWC data. All of these findings and their clinical implications are discussed, providing strong support for the reliability of LENA in French.

Pre-Proposal Assessment of Reliability for Spacecraft Docking with Limited Information

NASA Technical Reports Server (NTRS)

Brall, Aron

2013-01-01

This paper addresses the problem of estimating the reliability of a critical system function as well as its impact on the system reliability when limited information is available. The approach addresses the basic function reliability, and then the impact of multiple attempts to accomplish the function. The dependence of subsequent attempts on prior failure to accomplish the function is also addressed. The autonomous docking of two spacecraft was the specific example that generated the inquiry, and the resultant impact on total reliability generated substantial interest in presenting the results due to the relative insensitivity of overall performance to basic function reliability and moderate degradation given sufficient attempts to try and accomplish the required goal. The application of the methodology allows proper emphasis on the characteristics that can be estimated with some knowledge, and to insulate the integrity of the design from those characteristics that can't be properly estimated with any rational value of uncertainty. The nature of NASA's missions contains a great deal of uncertainty due to the pursuit of new science or operations. This approach can be applied to any function where multiple attempts at success, with or without degradation, are allowed.

Reliability analysis of composite structures

NASA Technical Reports Server (NTRS)

Kan, Han-Pin

1992-01-01

A probabilistic static stress analysis methodology has been developed to estimate the reliability of a composite structure. Closed form stress analysis methods are the primary analytical tools used in this methodology. These structural mechanics methods are used to identify independent variables whose variations significantly affect the performance of the structure. Once these variables are identified, scatter in their values is evaluated and statistically characterized. The scatter in applied loads and the structural parameters are then fitted to appropriate probabilistic distribution functions. Numerical integration techniques are applied to compute the structural reliability. The predicted reliability accounts for scatter due to variability in material strength, applied load, fabrication and assembly processes. The influence of structural geometry and mode of failure are also considerations in the evaluation. Example problems are given to illustrate various levels of analytical complexity.

The Balanced Inventory of Desirable Responding (BIDR): A Reliability Generalization Study

ERIC Educational Resources Information Center

Li, Andrew; Bagger, Jessica

2007-01-01

The Balanced Inventory of Desirable Responding (BIDR) is one of the most widely used social desirability scales. The authors conducted a reliability generalization study to examine the typical reliability coefficients of BIDR scores and explored factors that explained the variability of reliability estimates across studies. The results indicated…

Reliability of environmental sampling culture results using the negative binomial intraclass correlation coefficient.

PubMed

Aly, Sharif S; Zhao, Jianyang; Li, Ben; Jiang, Jiming

2014-01-01

The Intraclass Correlation Coefficient (ICC) is commonly used to estimate the similarity between quantitative measures obtained from different sources. Overdispersed data is traditionally transformed so that linear mixed model (LMM) based ICC can be estimated. A common transformation used is the natural logarithm. The reliability of environmental sampling of fecal slurry on freestall pens has been estimated for Mycobacterium avium subsp. paratuberculosis using the natural logarithm transformed culture results. Recently, the negative binomial ICC was defined based on a generalized linear mixed model for negative binomial distributed data. The current study reports on the negative binomial ICC estimate which includes fixed effects using culture results of environmental samples. Simulations using a wide variety of inputs and negative binomial distribution parameters (r; p) showed better performance of the new negative binomial ICC compared to the ICC based on LMM even when negative binomial data was logarithm, and square root transformed. A second comparison that targeted a wider range of ICC values showed that the mean of estimated ICC closely approximated the true ICC.

Resting State Network Estimation in Individual Subjects

PubMed Central

Hacker, Carl D.; Laumann, Timothy O.; Szrama, Nicholas P.; Baldassarre, Antonello; Snyder, Abraham Z.

2014-01-01

Resting-state functional magnetic resonance imaging (fMRI) has been used to study brain networks associated with both normal and pathological cognitive function. The objective of this work is to reliably compute resting state network (RSN) topography in single participants. We trained a supervised classifier (multi-layer perceptron; MLP) to associate blood oxygen level dependent (BOLD) correlation maps corresponding to pre-defined seeds with specific RSN identities. Hard classification of maps obtained from a priori seeds was highly reliable across new participants. Interestingly, continuous estimates of RSN membership retained substantial residual error. This result is consistent with the view that RSNs are hierarchically organized, and therefore not fully separable into spatially independent components. After training on a priori seed-based maps, we propagated voxel-wise correlation maps through the MLP to produce estimates of RSN membership throughout the brain. The MLP generated RSN topography estimates in individuals consistent with previous studies, even in brain regions not represented in the training data. This method could be used in future studies to relate RSN topography to other measures of functional brain organization (e.g., task-evoked responses, stimulation mapping, and deficits associated with lesions) in individuals. The multi-layer perceptron was directly compared to two alternative voxel classification procedures, specifically, dual regression and linear discriminant analysis; the perceptron generated more spatially specific RSN maps than either alternative. PMID:23735260

Trapping Elusive Cats: Using Intensive Camera Trapping to Estimate the Density of a Rare African Felid

PubMed Central

Brassine, Eléanor; Parker, Daniel

2015-01-01

Camera trapping studies have become increasingly popular to produce population estimates of individually recognisable mammals. Yet, monitoring techniques for rare species which occur at extremely low densities are lacking. Additionally, species which have unpredictable movements may make obtaining reliable population estimates challenging due to low detectability. Our study explores the effectiveness of intensive camera trapping for estimating cheetah (Acinonyx jubatus) numbers. Using both a more traditional, systematic grid approach and pre-determined, targeted sites for camera placement, the cheetah population of the Northern Tuli Game Reserve, Botswana was sampled between December 2012 and October 2013. Placement of cameras in a regular grid pattern yielded very few (n = 9) cheetah images and these were insufficient to estimate cheetah density. However, pre-selected cheetah scent-marking posts provided 53 images of seven adult cheetahs (0.61 ± 0.18 cheetahs/100km²). While increasing the length of the camera trapping survey from 90 to 130 days increased the total number of cheetah images obtained (from 53 to 200), no new individuals were recorded and the estimated population density remained stable. Thus, our study demonstrates that targeted camera placement (irrespective of survey duration) is necessary for reliably assessing cheetah densities where populations are naturally very low or dominated by transient individuals. Significantly our approach can easily be applied to other rare predator species. PMID:26698574

Trapping Elusive Cats: Using Intensive Camera Trapping to Estimate the Density of a Rare African Felid.

PubMed

Brassine, Eléanor; Parker, Daniel

2015-01-01

Camera trapping studies have become increasingly popular to produce population estimates of individually recognisable mammals. Yet, monitoring techniques for rare species which occur at extremely low densities are lacking. Additionally, species which have unpredictable movements may make obtaining reliable population estimates challenging due to low detectability. Our study explores the effectiveness of intensive camera trapping for estimating cheetah (Acinonyx jubatus) numbers. Using both a more traditional, systematic grid approach and pre-determined, targeted sites for camera placement, the cheetah population of the Northern Tuli Game Reserve, Botswana was sampled between December 2012 and October 2013. Placement of cameras in a regular grid pattern yielded very few (n = 9) cheetah images and these were insufficient to estimate cheetah density. However, pre-selected cheetah scent-marking posts provided 53 images of seven adult cheetahs (0.61 ± 0.18 cheetahs/100 km²). While increasing the length of the camera trapping survey from 90 to 130 days increased the total number of cheetah images obtained (from 53 to 200), no new individuals were recorded and the estimated population density remained stable. Thus, our study demonstrates that targeted camera placement (irrespective of survey duration) is necessary for reliably assessing cheetah densities where populations are naturally very low or dominated by transient individuals. Significantly our approach can easily be applied to other rare predator species.

Gas-hydrate concentration estimated from P- and S-wave velocities at the Mallik 2L-38 research well, Mackenzie Delta, Canada

NASA Astrophysics Data System (ADS)

Carcione, José M.; Gei, Davide

2004-05-01

We estimate the concentration of gas hydrate at the Mallik 2L-38 research site using P- and S-wave velocities obtained from well logging and vertical seismic profiles (VSP). The theoretical velocities are obtained from a generalization of Gassmann's modulus to three phases (rock frame, gas hydrate and fluid). The dry-rock moduli are estimated from the log profiles, in sections where the rock is assumed to be fully saturated with water. We obtain hydrate concentrations up to 75%, average values of 37% and 21% from the VSP P- and S-wave velocities, respectively, and 60% and 57% from the sonic-log P- and S-wave velocities, respectively. The above averages are similar to estimations obtained from hydrate dissociation modeling and Archie methods. The estimations based on the P-wave velocities are more reliable than those based on the S-wave velocities.

A Direct Method for Obtaining Approximate Standard Error and Confidence Interval of Maximal Reliability for Composites with Congeneric Measures

ERIC Educational Resources Information Center

Raykov, Tenko; Penev, Spiridon

2006-01-01

Unlike a substantial part of reliability literature in the past, this article is concerned with weighted combinations of a given set of congeneric measures with uncorrelated errors. The relationship between maximal coefficient alpha and maximal reliability for such composites is initially dealt with, and it is shown that the former is a lower…

Using Internet search engines to estimate word frequency.

PubMed

Blair, Irene V; Urland, Geoffrey R; Ma, Jennifer E

2002-05-01

The present research investigated Internet search engines as a rapid, cost-effective alternative for estimating word frequencies. Frequency estimates for 382 words were obtained and compared across four methods: (1) Internet search engines, (2) the Kucera and Francis (1967) analysis of a traditional linguistic corpus, (3) the CELEX English linguistic database (Baayen, Piepenbrock, & Gulikers, 1995), and (4) participant ratings of familiarity. The results showed that Internet search engines produced frequency estimates that were highly consistent with those reported by Kucera and Francis and those calculated from CELEX, highly consistent across search engines, and very reliable over a 6-month period of time. Additional results suggested that Internet search engines are an excellent option when traditional word frequency analyses do not contain the necessary data (e.g., estimates for forenames and slang). In contrast, participants' familiarity judgments did not correspond well with the more objective estimates of word frequency. Researchers are advised to use search engines with large databases (e.g., AltaVista) to ensure the greatest representativeness of the frequency estimates.

Highly reliable oxide VCSELs for datacom applications

NASA Astrophysics Data System (ADS)

Aeby, Ian; Collins, Doug; Gibson, Brian; Helms, Christopher J.; Hou, Hong Q.; Lou, Wenlin; Bossert, David J.; Wang, Charlie X.

2003-06-01

In this paper we describe the processes and procedures that have been developed to ensure high reliability for Emcore"s 850 nm oxide confined GaAs VCSELs. Evidence from on-going accelerated life testing and other reliability studies that confirm that this process yields reliable products will be discussed. We will present data and analysis techniques used to determine the activation energy and acceleration factors for the dominant wear-out failure mechanisms for our devices as well as our estimated MTTF of greater than 2 million use hours. We conclude with a summary of internal verification and field return rate validation data.

Reliability of CKD-EPI predictive equation in estimating chronic kidney disease prevalence in the Croatian endemic nephropathy area

PubMed Central

Fuček, Mirjana; Dika, Živka; Karanović, Sandra; Vuković Brinar, Ivana; Premužić, Vedran; Kos, Jelena; Cvitković, Ante; Mišić, Maja; Samardžić, Josip; Rogić, Dunja; Jelaković, Bojan

2017-01-01

Introduction Chronic kidney disease (CKD) is a significant public health problem and it is not possible to precisely predict its progression to terminal renal failure. According to current guidelines, CKD stages are classified based on the estimated glomerular filtration rate (eGFR) and albuminuria. Aims of this study were to determine the reliability of predictive equation in estimation of CKD prevalence in Croatian areas with endemic nephropathy (EN), compare the results with non-endemic areas, and to determine if the prevalence of CKD stages 3-5 was increased in subjects with EN. Materials and methods A total of 1573 inhabitants of the Croatian Posavina rural area from 6 endemic and 3 non-endemic villages were enrolled. Participants were classified according to the modified criteria of the World Health Organization for EN. Estimated GFR was calculated using Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI). Results The results showed a very high CKD prevalence in the Croatian rural area (19%). CKD prevalence was significantly higher in EN then in non EN villages with the lowest eGFR value in diseased subgroup. Conclusions eGFR correlated significantly with the diagnosis of EN. Kidney function assessment using CKD-EPI predictive equation proved to be a good marker in differentiating the study subgroups, remained as one of the diagnostic criteria for EN. PMID:29187794

An analysis of estimation of pulmonary blood flow by the single-breath method

NASA Technical Reports Server (NTRS)

Srinivasan, R.

1986-01-01

The single-breath method represents a simple noninvasive technique for the assessment of capillary blood flow across the lung. However, this method has not gained widespread acceptance, because its accuracy is still being questioned. A rigorous procedure is described for estimating pulmonary blood flow (PBF) using data obtained with the aid of the single-breath method. Attention is given to the minimization of data-processing errors in the presence of measurement errors and to questions regarding a correction for possible loss of CO2 in the lung tissue. It is pointed out that the estimations are based on the exact solution of the underlying differential equations which describe the dynamics of gas exchange in the lung. The reported study demonstrates the feasibility of obtaining highly reliable estimates of PBF from expiratory data in the presence of random measurement errors.

Uncertainty Estimates of Psychoacoustic Thresholds Obtained from Group Tests

NASA Technical Reports Server (NTRS)

Rathsam, Jonathan; Christian, Andrew

2016-01-01

Adaptive psychoacoustic test methods, in which the next signal level depends on the response to the previous signal, are the most efficient for determining psychoacoustic thresholds of individual subjects. In many tests conducted in the NASA psychoacoustic labs, the goal is to determine thresholds representative of the general population. To do this economically, non-adaptive testing methods are used in which three or four subjects are tested at the same time with predetermined signal levels. This approach requires us to identify techniques for assessing the uncertainty in resulting group-average psychoacoustic thresholds. In this presentation we examine the Delta Method of frequentist statistics, the Generalized Linear Model (GLM), the Nonparametric Bootstrap, a frequentist method, and Markov Chain Monte Carlo Posterior Estimation and a Bayesian approach. Each technique is exercised on a manufactured, theoretical dataset and then on datasets from two psychoacoustics facilities at NASA. The Delta Method is the simplest to implement and accurate for the cases studied. The GLM is found to be the least robust, and the Bootstrap takes the longest to calculate. The Bayesian Posterior Estimate is the most versatile technique examined because it allows the inclusion of prior information.

Objectivity and validity of EMG method in estimating anaerobic threshold.

PubMed

Kang, S-K; Kim, J; Kwon, M; Eom, H

2014-08-01

The purposes of this study were to verify and compare the performances of anaerobic threshold (AT) point estimates among different filtering intervals (9, 15, 20, 25, 30 s) and to investigate the interrelationships of AT point estimates obtained by ventilatory threshold (VT) and muscle fatigue thresholds using electromyographic (EMG) activity during incremental exercise on a cycle ergometer. 69 untrained male university students, yet pursuing regular exercise voluntarily participated in this study. The incremental exercise protocol was applied with a consistent stepwise increase in power output of 20 watts per minute until exhaustion. AT point was also estimated in the same manner using V-slope program with gas exchange parameters. In general, the estimated values of AT point-time computed by EMG method were more consistent across 5 filtering intervals and demonstrated higher correlations among themselves when compared with those values obtained by VT method. The results found in the present study suggest that the EMG signals could be used as an alternative or a new option in estimating AT point. Also the proposed computing procedure implemented in Matlab for the analysis of EMG signals appeared to be valid and reliable as it produced nearly identical values and high correlations with VT estimates. © Georg Thieme Verlag KG Stuttgart · New York.

A robust motion estimation system for minimal invasive laparoscopy

NASA Astrophysics Data System (ADS)

Marcinczak, Jan Marek; von Öhsen, Udo; Grigat, Rolf-Rainer

2012-02-01

Laparoscopy is a reliable imaging method to examine the liver. However, due to the limited field of view, a lot of experience is required from the surgeon to interpret the observed anatomy. Reconstruction of organ surfaces provide valuable additional information to the surgeon for a reliable diagnosis. Without an additional external tracking system the structure can be recovered from feature correspondences between different frames. In laparoscopic images blurred frames, specular reflections and inhomogeneous illumination make feature tracking a challenging task. We propose an ego-motion estimation system for minimal invasive laparoscopy that can cope with specular reflection, inhomogeneous illumination and blurred frames. To obtain robust feature correspondence, the approach combines SIFT and specular reflection segmentation with a multi-frame tracking scheme. The calibrated five-point algorithm is used with the MSAC robust estimator to compute the motion of the endoscope from multi-frame correspondence. The algorithm is evaluated using endoscopic videos of a phantom. The small incisions and the rigid endoscope limit the motion in minimal invasive laparoscopy. These limitations are considered in our evaluation and are used to analyze the accuracy of pose estimation that can be achieved by our approach. The endoscope is moved by a robotic system and the ground truth motion is recorded. The evaluation on typical endoscopic motion gives precise results and demonstrates the practicability of the proposed pose estimation system.

Reliability of provocative tests of motion sickness susceptibility

NASA Technical Reports Server (NTRS)

Calkins, D. S.; Reschke, M. F.; Kennedy, R. S.; Dunlop, W. P.

1987-01-01

Test-retest reliability values were derived from motion sickness susceptibility scores obtained from two successive exposures to each of three tests: (1) Coriolis sickness sensitivity test; (2) staircase velocity movement test; and (3) parabolic flight static chair test. The reliability of the three tests ranged from 0.70 to 0.88. Normalizing values from predictors with skewed distributions improved the reliability.

Reliability and concurrent validity of Futrex and bioelectrical impedance.

PubMed

Vehrs, P; Morrow, J R; Butte, N

1998-11-01

Thirty Caucasian males (aged 19-32yr) participated in this study designed to investigate the reliability of multiple bioelectrical impedance analysis (BIA) and near-infrared spectroscopy (Futrex, FTX) measurements and the validity of BIA and FTX estimations of hydrostatically (UW) determined percent body fat (%BF). Two BIA and two FTX instruments were used to make 6 measurements each of resistance (R) and optical density (OD) respectively over a 30 min period on two consecutive days. Repeated measures ANOVA indicated that FTX and BIA, using manufacturer's equations, significantly (p<0.01) under predicted UW by 2.4 and 3.8%BF respectively. Standard error of estimate (SEE) and total error (TE) terms provided by regression analysis for FTX (4.6 and 5.31%BF respectively) and BIA (5.65 and 6.95%BF, respectively) were high. Dependent t-tests revealed no significant differences in either FTX or BIA predictions of %BF using two machines. Intraclass reliabilities for BIA and FTX estimates of UW %BF across trials, days, and machines all exceeded 0.97. A significant random error term associated with FTX and a significant subject-by-day interaction associated with BIA was revealed using the generalizability model. Although FTX and BIA estimates of UW %BF were reliable, due to the significant underestimation of UW %BF and high SEE and TE, neither FTX nor BIA were considered valid estimates of hydrostatically determined %BF.

Malthusian Parameters as Estimators of the Fitness of Microbes: A Cautionary Tale about the Low Side of High Throughput.

PubMed

Concepción-Acevedo, Jeniffer; Weiss, Howard N; Chaudhry, Waqas Nasir; Levin, Bruce R

2015-01-01

The maximum exponential growth rate, the Malthusian parameter (MP), is commonly used as a measure of fitness in experimental studies of adaptive evolution and of the effects of antibiotic resistance and other genes on the fitness of planktonic microbes. Thanks to automated, multi-well optical density plate readers and computers, with little hands-on effort investigators can readily obtain hundreds of estimates of MPs in less than a day. Here we compare estimates of the relative fitness of antibiotic susceptible and resistant strains of E. coli, Pseudomonas aeruginosa and Staphylococcus aureus based on MP data obtained with automated multi-well plate readers with the results from pairwise competition experiments. This leads us to question the reliability of estimates of MP obtained with these high throughput devices and the utility of these estimates of the maximum growth rates to detect fitness differences.

Evaluation of reliability modeling tools for advanced fault tolerant systems

NASA Technical Reports Server (NTRS)

Baker, Robert; Scheper, Charlotte

1986-01-01

The Computer Aided Reliability Estimation (CARE III) and Automated Reliability Interactice Estimation System (ARIES 82) reliability tools for application to advanced fault tolerance aerospace systems were evaluated. To determine reliability modeling requirements, the evaluation focused on the Draper Laboratories' Advanced Information Processing System (AIPS) architecture as an example architecture for fault tolerance aerospace systems. Advantages and limitations were identified for each reliability evaluation tool. The CARE III program was designed primarily for analyzing ultrareliable flight control systems. The ARIES 82 program's primary use was to support university research and teaching. Both CARE III and ARIES 82 were not suited for determining the reliability of complex nodal networks of the type used to interconnect processing sites in the AIPS architecture. It was concluded that ARIES was not suitable for modeling advanced fault tolerant systems. It was further concluded that subject to some limitations (the difficulty in modeling systems with unpowered spare modules, systems where equipment maintenance must be considered, systems where failure depends on the sequence in which faults occurred, and systems where multiple faults greater than a double near coincident faults must be considered), CARE III is best suited for evaluating the reliability of advanced tolerant systems for air transport.

Measuring acuity of the approximate number system reliably and validly: the evaluation of an adaptive test procedure

PubMed Central

Lindskog, Marcus; Winman, Anders; Juslin, Peter; Poom, Leo

2013-01-01

Two studies investigated the reliability and predictive validity of commonly used measures and models of Approximate Number System acuity (ANS). Study 1 investigated reliability by both an empirical approach and a simulation of maximum obtainable reliability under ideal conditions. Results showed that common measures of the Weber fraction (w) are reliable only when using a substantial number of trials, even under ideal conditions. Study 2 compared different purported measures of ANS acuity as for convergent and predictive validity in a within-subjects design and evaluated an adaptive test using the ZEST algorithm. Results showed that the adaptive measure can reduce the number of trials needed to reach acceptable reliability. Only direct tests with non-symbolic numerosity discriminations of stimuli presented simultaneously were related to arithmetic fluency. This correlation remained when controlling for general cognitive ability and perceptual speed. Further, the purported indirect measure of ANS acuity in terms of the Numeric Distance Effect (NDE) was not reliable and showed no sign of predictive validity. The non-symbolic NDE for reaction time was significantly related to direct w estimates in a direction contrary to the expected. Easier stimuli were found to be more reliable, but only harder (7:8 ratio) stimuli contributed to predictive validity. PMID:23964256

The ventriloquist in periphery: impact of eccentricity-related reliability on audio-visual localization.

PubMed

Charbonneau, Geneviève; Véronneau, Marie; Boudrias-Fournier, Colin; Lepore, Franco; Collignon, Olivier

2013-10-28

The relative reliability of separate sensory estimates influences the way they are merged into a unified percept. We investigated how eccentricity-related changes in reliability of auditory and visual stimuli influence their integration across the entire frontal space. First, we surprisingly found that despite a strong decrease in auditory and visual unisensory localization abilities in periphery, the redundancy gain resulting from the congruent presentation of audio-visual targets was not affected by stimuli eccentricity. This result therefore contrasts with the common prediction that a reduction in sensory reliability necessarily induces an enhanced integrative gain. Second, we demonstrate that the visual capture of sounds observed with spatially incongruent audio-visual targets (ventriloquist effect) steadily decreases with eccentricity, paralleling a lowering of the relative reliability of unimodal visual over unimodal auditory stimuli in periphery. Moreover, at all eccentricities, the ventriloquist effect positively correlated with a weighted combination of the spatial resolution obtained in unisensory conditions. These findings support and extend the view that the localization of audio-visual stimuli relies on an optimal combination of auditory and visual information according to their respective spatial reliability. All together, these results evidence that the external spatial coordinates of multisensory events relative to an observer's body (e.g., eyes' or head's position) influence how this information is merged, and therefore determine the perceptual outcome.

Reliability models applicable to space telescope solar array assembly system

NASA Technical Reports Server (NTRS)

Patil, S. A.

1986-01-01

A complex system may consist of a number of subsystems with several components in series, parallel, or combination of both series and parallel. In order to predict how well the system will perform, it is necessary to know the reliabilities of the subsystems and the reliability of the whole system. The objective of the present study is to develop mathematical models of the reliability which are applicable to complex systems. The models are determined by assuming k failures out of n components in a subsystem. By taking k = 1 and k = n, these models reduce to parallel and series models; hence, the models can be specialized to parallel, series combination systems. The models are developed by assuming the failure rates of the components as functions of time and as such, can be applied to processes with or without aging effects. The reliability models are further specialized to Space Telescope Solar Arrray (STSA) System. The STSA consists of 20 identical solar panel assemblies (SPA's). The reliabilities of the SPA's are determined by the reliabilities of solar cell strings, interconnects, and diodes. The estimates of the reliability of the system for one to five years are calculated by using the reliability estimates of solar cells and interconnects given n ESA documents. Aging effects in relation to breaks in interconnects are discussed.

Earthquake magnitude estimation using the τ c and P d method for earthquake early warning systems

NASA Astrophysics Data System (ADS)

Jin, Xing; Zhang, Hongcai; Li, Jun; Wei, Yongxiang; Ma, Qiang

2013-10-01

Earthquake early warning (EEW) systems are one of the most effective ways to reduce earthquake disaster. Earthquake magnitude estimation is one of the most important and also the most difficult parts of the entire EEW system. In this paper, based on 142 earthquake events and 253 seismic records that were recorded by the KiK-net in Japan, and aftershocks of the large Wenchuan earthquake in Sichuan, we obtained earthquake magnitude estimation relationships using the τ c and P d methods. The standard variances of magnitude calculation of these two formulas are ±0.65 and ±0.56, respectively. The P d value can also be used to estimate the peak ground motion of velocity, then warning information can be released to the public rapidly, according to the estimation results. In order to insure the stability and reliability of magnitude estimation results, we propose a compatibility test according to the natures of these two parameters. The reliability of the early warning information is significantly improved though this test.

Metrics for Assessing the Reliability of a Telemedicine Remote Monitoring System

PubMed Central

Fox, Mark; Papadopoulos, Amy; Crump, Cindy

2013-01-01

Abstract Objective: The goal of this study was to assess using new metrics the reliability of a real-time health monitoring system in homes of older adults. Materials and Methods: The “MobileCare Monitor” system was installed into the homes of nine older adults >75 years of age for a 2-week period. The system consisted of a wireless wristwatch-based monitoring system containing sensors for location, temperature, and impacts and a “panic” button that was connected through a mesh network to third-party wireless devices (blood pressure cuff, pulse oximeter, weight scale, and a survey-administering device). To assess system reliability, daily phone calls instructed participants to conduct system tests and reminded them to fill out surveys and daily diaries. Phone reports and participant diary entries were checked against data received at a secure server. Results: Reliability metrics assessed overall system reliability, data concurrence, study effectiveness, and system usability. Except for the pulse oximeter, system reliability metrics varied between 73% and 92%. Data concurrence for proximal and distal readings exceeded 88%. System usability following the pulse oximeter firmware update varied between 82% and 97%. An estimate of watch-wearing adherence within the home was quite high, about 80%, although given the inability to assess watch-wearing when a participant left the house, adherence likely exceeded the 10 h/day requested time. In total, 3,436 of 3,906 potential measurements were obtained, indicating a study effectiveness of 88%. Conclusions: The system was quite effective in providing accurate remote health data. The different system reliability measures identify important error sources in remote monitoring systems. PMID:23611640

Preoperative TRAM free flap volume estimation for breast reconstruction in lean patients.

PubMed

Minn, Kyung Won; Hong, Ki Yong; Lee, Sang Woo

2010-04-01

To obtain pleasing symmetry in breast reconstruction with transverse rectus abdominis myocutaneous (TRAM) free flap, a large amount of abdominal flap is elevated and remnant tissue is trimmed in most cases. However, elevation of abundant abdominal flap can cause excessive tension in donor site closure and increase the possibility of hypertrophic scarring especially in lean patients. The TRAM flap was divided into 4 zones in routine manner; the depth and dimension of the 4 zones were obtained using ultrasound and AutoCAD (Autodesk Inc., San Rafael, CA), respectively. The acquired numbers were then multiplied to obtain an estimate of volume of each zone and the each zone volume was added. To confirm the relation between the estimated volume and the actual volume, authors compared intraoperative actual TRAM flap volumes with preoperative estimated volumes in 30 consecutive TRAM free flap breast reconstructions. The estimated volumes and the actual elevated volumes of flap were found to be correlated by regression analysis (r = 0.9258, P < 0.01). According to this result, we could confirm the reliability of the preoperative volume estimation using our method. Afterward, the authors applied this method to 7 lean patients by estimation and revision of the design and obtained symmetric results with minimal donor site morbidity. Preoperative estimation of TRAM flap volume with ultrasound and AutoCAD (Autodesk Inc.) allow the authors to attain the precise volume desired for elevation. This method provides advantages in terms of minimal flap trimming, easier closure of donor sites, reduced scar widening and symmetry, especially in lean patients.

Greenhouse gases inventory and carbon balance of two dairy systems obtained from two methane-estimation methods.

PubMed

Cunha, C S; Lopes, N L; Veloso, C M; Jacovine, L A G; Tomich, T R; Pereira, L G R; Marcondes, M I

2016-11-15

The adoption of carbon inventories for dairy farms in tropical countries based on models developed from animals and diets of temperate climates is questionable. Thus, the objectives of this study were to estimate enteric methane (CH4) emissions through the SF6 tracer gas technique and through equations proposed by the Intergovernmental Panel on Climate Change (IPCC) Tier 2 and to calculate the inventory of greenhouse gas (GHG) emissions from two dairy systems. In addition, the carbon balance of these properties was estimated using enteric CH4 emissions obtained using both methodologies. In trial 1, the CH4 emissions were estimated from seven Holstein dairy cattle categories based on the SF6 tracer gas technique and on IPCC equations. The categories used in the study were prepubertal heifers (n=6); pubertal heifers (n=4); pregnant heifers (n=5); high-producing (n=6); medium-producing (n=5); low-producing (n=4) and dry cows (n=5). Enteric methane emission was higher for the category comprising prepubertal heifers when estimated by the equations proposed by the IPCC Tier 2. However, higher CH4 emissions were estimated by the SF6 technique in the categories including medium- and high-producing cows and dry cows. Pubertal heifers, pregnant heifers, and low-producing cows had equal CH4 emissions as estimated by both methods. In trial 2, two dairy farms were monitored for one year to identify all activities that contributed in any way to GHG emissions. The total emission from Farm 1 was 3.21t CO2e/animal/yr, of which 1.63t corresponded to enteric CH4. Farm 2 emitted 3.18t CO2e/animal/yr, with 1.70t of enteric CH4. IPCC estimations can underestimate CH4 emissions from some categories while overestimate others. However, considering the whole property, these discrepancies are offset and we would submit that the equations suggested by the IPCC properly estimate the total CH4 emission and carbon balance of the properties. Thus, the IPCC equations should be utilized with

Statistical Bayesian method for reliability evaluation based on ADT data

NASA Astrophysics Data System (ADS)

Lu, Dawei; Wang, Lizhi; Sun, Yusheng; Wang, Xiaohong

2018-05-01

Accelerated degradation testing (ADT) is frequently conducted in the laboratory to predict the products’ reliability under normal operating conditions. Two kinds of methods, degradation path models and stochastic process models, are utilized to analyze degradation data and the latter one is the most popular method. However, some limitations like imprecise solution process and estimation result of degradation ratio still exist, which may affect the accuracy of the acceleration model and the extrapolation value. Moreover, the conducted solution of this problem, Bayesian method, lose key information when unifying the degradation data. In this paper, a new data processing and parameter inference method based on Bayesian method is proposed to handle degradation data and solve the problems above. First, Wiener process and acceleration model is chosen; Second, the initial values of degradation model and parameters of prior and posterior distribution under each level is calculated with updating and iteration of estimation values; Third, the lifetime and reliability values are estimated on the basis of the estimation parameters; Finally, a case study is provided to demonstrate the validity of the proposed method. The results illustrate that the proposed method is quite effective and accuracy in estimating the lifetime and reliability of a product.

Test-retest reliability of effective connectivity in the face perception network.

PubMed

Frässle, Stefan; Paulus, Frieder Michel; Krach, Sören; Jansen, Andreas

2016-02-01

Computational approaches have great potential for moving neuroscience toward mechanistic models of the functional integration among brain regions. Dynamic causal modeling (DCM) offers a promising framework for inferring the effective connectivity among brain regions and thus unraveling the neural mechanisms of both normal cognitive function and psychiatric disorders. While the benefit of such approaches depends heavily on their reliability, systematic analyses of the within-subject stability are rare. Here, we present a thorough investigation of the test-retest reliability of an fMRI paradigm for DCM analysis dedicated to unraveling intra- and interhemispheric integration among the core regions of the face perception network. First, we examined the reliability of face-specific BOLD activity in 25 healthy volunteers, who performed a face perception paradigm in two separate sessions. We found good to excellent reliability of BOLD activity within the DCM-relevant regions. Second, we assessed the stability of effective connectivity among these regions by analyzing the reliability of Bayesian model selection and model parameter estimation in DCM. Reliability was excellent for the negative free energy and good for model parameter estimation, when restricting the analysis to parameters with substantial effect sizes. Third, even when the experiment was shortened, reliability of BOLD activity and DCM results dropped only slightly as a function of the length of the experiment. This suggests that the face perception paradigm presented here provides reliable estimates for both conventional activation and effective connectivity measures. We conclude this paper with an outlook on potential clinical applications of the paradigm for studying psychiatric disorders. Hum Brain Mapp 37:730-744, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

On modeling human reliability in space flights - Redundancy and recovery operations

NASA Astrophysics Data System (ADS)

Aarset, M.; Wright, J. F.

The reliability of humans is of paramount importance to the safety of space flight systems. This paper describes why 'back-up' operators might not be the best solution, and in some cases, might even degrade system reliability. The problem associated with human redundancy calls for special treatment in reliability analyses. The concept of Standby Redundancy is adopted, and psychological and mathematical models are introduced to improve the way such problems can be estimated and handled. In the past, human reliability has practically been neglected in most reliability analyses, and, when included, the humans have been modeled as a component and treated numerically the way technical components are. This approach is not wrong in itself, but it may lead to systematic errors if too simple analogies from the technical domain are used in the modeling of human behavior. In this paper redundancy in a man-machine system will be addressed. It will be shown how simplification from the technical domain, when applied to human components of a system, may give non-conservative estimates of system reliability.

Time Domain Estimation of Arterial Parameters using the Windkessel Model and the Monte Carlo Method

NASA Astrophysics Data System (ADS)

Gostuski, Vladimir; Pastore, Ignacio; Rodriguez Palacios, Gaspar; Vaca Diez, Gustavo; Moscoso-Vasquez, H. Marcela; Risk, Marcelo

2016-04-01

Numerous parameter estimation techniques exist for characterizing the arterial system using electrical circuit analogs. However, they are often limited by their requirements and usually high computational burdain. Therefore, a new method for estimating arterial parameters based on Monte Carlo simulation is proposed. A three element Windkessel model was used to represent the arterial system. The approach was to reduce the error between the calculated and physiological aortic pressure by randomly generating arterial parameter values, while keeping constant the arterial resistance. This last value was obtained for each subject using the arterial flow, and was a necessary consideration in order to obtain a unique set of values for the arterial compliance and peripheral resistance. The estimation technique was applied to in vivo data containing steady beats in mongrel dogs, and it reliably estimated Windkessel arterial parameters. Further, this method appears to be computationally efficient for on-line time-domain estimation of these parameters.

The influence of different error estimates in the detection of postoperative cognitive dysfunction using reliable change indices with correction for practice effects.

PubMed

Lewis, Matthew S; Maruff, Paul; Silbert, Brendan S; Evered, Lis A; Scott, David A

2007-02-01

The reliable change index (RCI) expresses change relative to its associated error, and is useful in the identification of postoperative cognitive dysfunction (POCD). This paper examines four common RCIs that each account for error in different ways. Three rules incorporate a constant correction for practice effects and are contrasted with the standard RCI that had no correction for practice. These rules are applied to 160 patients undergoing coronary artery bypass graft (CABG) surgery who completed neuropsychological assessments preoperatively and 1 week postoperatively using error and reliability data from a comparable healthy nonsurgical control group. The rules all identify POCD in a similar proportion of patients, but the use of the within-subject standard deviation (WSD), expressing the effects of random error, as an error estimate is a theoretically appropriate denominator when a constant error correction, removing the effects of systematic error, is deducted from the numerator in a RCI.

Culture Representation in Human Reliability Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

David Gertman; Julie Marble; Steven Novack

Understanding human-system response is critical to being able to plan and predict mission success in the modern battlespace. Commonly, human reliability analysis has been used to predict failures of human performance in complex, critical systems. However, most human reliability methods fail to take culture into account. This paper takes an easily understood state of the art human reliability analysis method and extends that method to account for the influence of culture, including acceptance of new technology, upon performance. The cultural parameters used to modify the human reliability analysis were determined from two standard industry approaches to cultural assessment: Hofstede’s (1991)more » cultural factors and Davis’ (1989) technology acceptance model (TAM). The result is called the Culture Adjustment Method (CAM). An example is presented that (1) reviews human reliability assessment with and without cultural attributes for a Supervisory Control and Data Acquisition (SCADA) system attack, (2) demonstrates how country specific information can be used to increase the realism of HRA modeling, and (3) discusses the differences in human error probability estimates arising from cultural differences.« less

The Americleft Speech Project: A Training and Reliability Study.

PubMed

Chapman, Kathy L; Baylis, Adriane; Trost-Cardamone, Judith; Cordero, Kelly Nett; Dixon, Angela; Dobbelsteyn, Cindy; Thurmes, Anna; Wilson, Kristina; Harding-Bell, Anne; Sweeney, Triona; Stoddard, Gregory; Sell, Debbie

2016-01-01

To describe the results of two reliability studies and to assess the effect of training on interrater reliability scores. The first study (1) examined interrater and intrarater reliability scores (weighted and unweighted kappas) and (2) compared interrater reliability scores before and after training on the use of the Cleft Audit Protocol for Speech-Augmented (CAPS-A) with British English-speaking children. The second study examined interrater and intrarater reliability on a modified version of the CAPS-A (CAPS-A Americleft Modification) with American and Canadian English-speaking children. Finally, comparisons were made between the interrater and intrarater reliability scores obtained for Study 1 and Study 2. The participants were speech-language pathologists from the Americleft Speech Project. In Study 1, interrater reliability scores improved for 6 of the 13 parameters following training on the CAPS-A protocol. Comparison of the reliability results for the two studies indicated lower scores for Study 2 compared with Study 1. However, this appeared to be an artifact of the kappa statistic that occurred due to insufficient variability in the reliability samples for Study 2. When percent agreement scores were also calculated, the ratings appeared similar across Study 1 and Study 2. The findings of this study suggested that improvements in interrater reliability could be obtained following a program of systematic training. However, improvements were not uniform across all parameters. Acceptable levels of reliability were achieved for those parameters most important for evaluation of velopharyngeal function.

Reliability of the Fox-walk test in patients with rheumatoid arthritis.

PubMed

Verberkt, Cornelia Antonia; Fridén, Cecilia; Grooten, Wilhelmus Johannes Andreas; Opava, Christina H

2012-01-01

The Fox-walk test is a new method used to estimate aerobic capacity outside a clinical environment, which may be useful in the implementation of daily health-enhancing physical activity. The aim of our study was to investigate the reliability of the test in people with rheumatoid arthritis (RA). Fifteen participants performed the Fox-walk test three times with weekly intervals. The intraclass correlation coefficient (ICC), the standard error of measurement (SEM) and the smallest detectable change (SDC) were used to estimate the reliability. General health perception, lower limb pain and fatigue were measured to determine their potential influence on the reliability. There were no systematic differences between the three test occasions (p = 0.190) and the reliability was almost perfect (ICC = 0.982). None of the covariates influenced the reliability. The SEM was 0.999 ml/kg/min or 3.4% and the SDC was 2.769 ml/kg/min or 9.4%. These findings demonstrate that the Fox-walk test is reliable in people with RA and enables differentiation between people with RA and monitoring progress. The validity of the test among people with RA is still to be determined. • The Fox-walk test is a new method to estimate aerobic capacity and could be performed walking or running. • The test is self administered without expensive equipment and is available in 150 public places in Sweden and several other European countries. • The Fox-walk test is a reliable test for use among people with rheumatoid arthritis monitoring the progress of their physical activity.

Application of a truncated normal failure distribution in reliability testing

NASA Technical Reports Server (NTRS)

Groves, C., Jr.

1968-01-01

Statistical truncated normal distribution function is applied as a time-to-failure distribution function in equipment reliability estimations. Age-dependent characteristics of the truncated function provide a basis for formulating a system of high-reliability testing that effectively merges statistical, engineering, and cost considerations.

Psychometric Properties of IRT Proficiency Estimates

ERIC Educational Resources Information Center

Kolen, Michael J.; Tong, Ye

2010-01-01

Psychometric properties of item response theory proficiency estimates are considered in this paper. Proficiency estimators based on summed scores and pattern scores include non-Bayes maximum likelihood and test characteristic curve estimators and Bayesian estimators. The psychometric properties investigated include reliability, conditional…

Effect of Small Numbers of Test Results on Accuracy of Hoek-Brown Strength Parameter Estimations: A Statistical Simulation Study

NASA Astrophysics Data System (ADS)

Bozorgzadeh, Nezam; Yanagimura, Yoko; Harrison, John P.

2017-12-01

The Hoek-Brown empirical strength criterion for intact rock is widely used as the basis for estimating the strength of rock masses. Estimations of the intact rock H-B parameters, namely the empirical constant m and the uniaxial compressive strength σc, are commonly obtained by fitting the criterion to triaxial strength data sets of small sample size. This paper investigates how such small sample sizes affect the uncertainty associated with the H-B parameter estimations. We use Monte Carlo (MC) simulation to generate data sets of different sizes and different combinations of H-B parameters, and then investigate the uncertainty in H-B parameters estimated from these limited data sets. We show that the uncertainties depend not only on the level of variability but also on the particular combination of parameters being investigated. As particular combinations of H-B parameters can informally be considered to represent specific rock types, we discuss that as the minimum number of required samples depends on rock type it should correspond to some acceptable level of uncertainty in the estimations. Also, a comparison of the results from our analysis with actual rock strength data shows that the probability of obtaining reliable strength parameter estimations using small samples may be very low. We further discuss the impact of this on ongoing implementation of reliability-based design protocols and conclude with suggestions for improvements in this respect.

Reliability of reference distances used in photogrammetry.