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Search Results: 1 - 10 of 833 matches for " Broemeling LD "
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Bayesian meta-analysis for test accuracy
Broemeling LD
Open Access Medical Statistics , 2011, DOI: http://dx.doi.org/10.2147/OAMS.S21499
Abstract: ayesian meta-analysis for test accuracy Original Research (2990) Total Article Views Authors: Broemeling LD Published Date September 2011 Volume 2011:1 Pages 21 - 35 DOI: http://dx.doi.org/10.2147/OAMS.S21499 Lyle D Broemeling Broemeling & Associates Inc, Medical Lake, WA, USA Abstract: Determining the accuracy of a medical test is quite difficult because accuracy is an elusive parameter to estimate. A common scenario is estimating the true and false positive fractions from different studies and arriving at a common value of the accuracy of the test. The accuracy is expressed with an estimate similar to the area under the receiver operating characteristic (ROC) curve. Under the assumption that the ROC area is the same across all tests, the true and false positive fractions can be plotted on the same graph to obtain an experimental ROC curve, called the summary ROC curve (SROC) curve. The estimate of the accuracy of the curve is the ordinate of the point of intersection, where the SROC curve intersects the line with equation true positive rate + false positive rate = 1. Using a Bayesian approach, the presentation begins with summarizing information about test accuracy for tests with ordinal and continuous scores, where it is assumed the tests share a common ROC curve, but the tests may differ in the threshold used to declare a positive test. The true and false positive rates are transformed so that one may use bilogistic regression to determine the accuracy of the combined tests where the posterior distribution of the parameters of the model are determined. Bayesian inferences are based on the posterior distribution of the SROC curve and the computations are executed with the WinBUGS software package, and several examples from various areas of medicine illustrate the methodology.
Bayesian meta-analysis for test accuracy
Broemeling LD
Open Access Medical Statistics , 2011,
Abstract: Lyle D BroemelingBroemeling & Associates Inc, Medical Lake, WA, USAAbstract: Determining the accuracy of a medical test is quite difficult because accuracy is an elusive parameter to estimate. A common scenario is estimating the true and false positive fractions from different studies and arriving at a common value of the accuracy of the test. The accuracy is expressed with an estimate similar to the area under the receiver operating characteristic (ROC) curve. Under the assumption that the ROC area is the same across all tests, the true and false positive fractions can be plotted on the same graph to obtain an experimental ROC curve, called the summary ROC curve (SROC) curve. The estimate of the accuracy of the curve is the ordinate of the point of intersection, where the SROC curve intersects the line with equation true positive rate + false positive rate = 1. Using a Bayesian approach, the presentation begins with summarizing information about test accuracy for tests with ordinal and continuous scores, where it is assumed the tests share a common ROC curve, but the tests may differ in the threshold used to declare a positive test. The true and false positive rates are transformed so that one may use bilogistic regression to determine the accuracy of the combined tests where the posterior distribution of the parameters of the model are determined. Bayesian inferences are based on the posterior distribution of the SROC curve and the computations are executed with the WinBUGS software package, and several examples from various areas of medicine illustrate the methodology.Keywords: Bayesian inferences, meta-analysis, SROC curve
Bayesian Estimation of Combined Accuracy for Tests with Verification Bias
Lyle D. Broemeling
Diagnostics , 2011, DOI: 10.3390/diagnostics1010053
Abstract: This presentation will emphasize the estimation of the combined accuracy of two or more tests when verification bias is present. Verification bias occurs when some of the subjects are not subject to the gold standard. The approach is Bayesian where the estimation of test accuracy is based on the posterior distribution of the relevant parameter. Accuracy of two combined binary tests is estimated employing either “believe the positive” or “believe the negative” rule, then the true and false positive fractions for each rule are computed for two tests. In order to perform the analysis, the missing at random assumption is imposed, and an interesting example is provided by estimating the combined accuracy of CT and MRI to diagnose lung cancer. The Bayesian approach is extended to two ordinal tests when verification bias is present, and the accuracy of the combined tests is based on the ROC area of the risk function. An example involving mammography with two readers with extreme verification bias illustrates the estimation of the combined test accuracy for ordinal tests.
Bayesian Methods for Medical Test Accuracy
Lyle D. Broemeling
Diagnostics , 2011, DOI: 10.3390/diagnostics1010001
Abstract: Bayesian methods for medical test accuracy are presented, beginning with the basic measures for tests with binary scores: true positive fraction, false positive fraction, positive predictive values, and negative predictive value. The Bayesian approach is taken because of its efficient use of prior information, and the analysis is executed with a Bayesian software package WinBUGS?. The ROC (receiver operating characteristic) curve gives the intrinsic accuracy of medical tests that have ordinal or continuous scores, and the Bayesian approach is illustrated with many examples from cancer and other diseases. Medical tests include X-ray, mammography, ultrasound, computed tomography, magnetic resonance imaging, nuclear medicine and tests based on biomarkers, such as blood glucose values for diabetes. The presentation continues with more specialized methods suitable for measuring the accuracies of clinical studies that have verification bias, and medical tests without a gold standard. Lastly, the review is concluded with Bayesian methods for measuring the accuracy of the combination of two or more tests.
The division and bending of green and red semiconductor laser light at the same time  [PDF]
Remzi Y?ld?r?m
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.310114
Abstract: In this experimental study, the laser light was split and bended using a specially designed glass lenses at the same time. This process has been done at the atmospheric pressure and room temperature conditions. During the experiments, the semiconductor laser as a source of green and red laser diode is used. In addition, polari- zation, magnetic field, electric field or any other auxiliary materials and systems which affect laser light are not used to bend the laser light. Only transparent glass lenses that are designed specially are used in the experimental study.
Benefaction from Carbonation of Flue Gas CO2 as Coal Mining Filling  [PDF]
Y?ld?r?m ?. Tosun
Geomaterials (GM) , 2014, DOI: 10.4236/gm.2014.42007
Abstract: CO2 capturing, transport and sequestration by pressurized water dissolution and reacting by natural alkali lime and magnesia in coal fly ash or other sources become an industrial advantageous sequestration option resulting in green waste solutions or solid fines. Mg and Ca containing minerals are reacting with CO2 to form carbonates. Various types of fly ash materials may react with CO2 to form carbonate regarding ash composition and reaction parameters. Mineral sequestration of CO2 will also allow using the products in cement industry or as cement material in constructions with low cost. This paper discussed progress on coal mining filling by carbonation method using coal fly ash of Soma, Yatagan, Afsin Elbistan Power Stations. Other filler materials containing coal mine waste shale, fly ashes and foam concrete, and additives were searched for pretreatment methods to enhance cement reactivity; and in analyzing the structural changes to identify reaction paths and potential barriers.
Shale Stone and Fly Ash Landfill Use in Landslide Hazardous Area in Sirnak City with Foam Concrete  [PDF]
Y?ld?r?m ?. Tosun
Geomaterials (GM) , 2014, DOI: 10.4236/gm.2014.44014
Abstract: Sirnak City and the surrounding areas are on steeper slopes. There are sliding large land masses or rocks. Underground water and harsh climatic conditions contain high risk hazard areas in urban living site with higher population density. In order to eliminate landslides and related events, significant precautions should be taken. The mapping of landslide risk may ease to take precautions. Even the application of landfill rock may reduce water content of soil. In this research, fly ash and Mine Waste shale stone were used with low density foam concrete. Waste mixture at certain proportions decreased cement use. Shale stone as fine aggregate instead of fly ash in specific proportions improved mechanical strength and porosity. Hence landslide hazardous area could be safer for urban living.
On Being a Juror: A Phenomenological Self-Study
LD Fortune
Indo-Pacific Journal of Phenomenology , 2009,
Abstract: Phenomenological inquiry offers a vehicle for transcending conventional disciplinary boundaries and investigative settings. Van Manen's protocol writing offers a hermeneutic tool for human scientific phenomenological research that is ideal for the empirical realm of everyday lived experience. Underlying this approach is the tenet that interpretative phenomenological research and theorizing cannot be separated from the textual practice of writing. The entirety of this paper is a protocol, in the form of a phenomenological self-study. It describes one experience in an unfamiliar environment as a criminal trial juror. It represents data capture that can stand alone for purposes of independent interpretation. Since qualitative research in the venue described is limited by protective judicial restrictions, this phenomenological protocol captures unique data in an otherwise inaccessible setting. It suggests that protocol writing offers potential as a research tool in a myriad situations where conventional data collection techniques are impractical or unavailable.
Metodologii de dezvoltare a sistemelor expert
Genete LD
Scientific Annals of the Alexandru Ioan Cuza University of Iasi : Economic Sciences Series , 2005,
Abstract:
Effective Used of Oncom Tofu By-Product as a Broiler Chicken Feedstuff
LD Mahfudz
Journal of Animal Production , 2006,
Abstract: A research was conducted to know affectivity of “oncom” of tofu by-product as a broiler chicken feedstuff, was done at Poultry Science Laboratory, Faculty of Animal Husbandry, Diponegoro University Semarang, from September until October 2002. Sixty broiler chick strain Arbor Acres at 1 week old, unsex with initial body weidht 120.08±15.58 g was used. Homogeneity test of material used Barlet Test consider of Sudjana (1996). The chicks was postal house litter system with long and wide 10 x 6 m2, open walls and roof from “genting”. The house was divided on 20 pen with bamboo stick by 1 x 0.75 x 0.75 m3 per pen. House was comleted by feeder and waterer, brooder and scale triple-beam “O Haust”. Tofu by-product was fermented by “oncom” yeast consist of Neurospora sp. Experimental feed based on yellow corn, rice polished, soybean, fish meal and mineral mix and tofu by-product. The feed was formulated with same protein and energy (equal protein and equal energy). The feed for first period with 22% protein and 2.900 kcal/kg, will the feed for last period with 20% protein and 3.000 kcal/kg. The treatment are tofu by-product fermentation as follow : T0, T1, T2 and T3 are 0, 10, 15 and 20% respectively. The parameters were feed consumption, body weight gain, feed conversion ratio, last body weight and carcass percentage. The Completely Randomized Design was used as Experiment design, consist of 4 treatment with 5 replication each, and every experimental unit consist of 3 birds. The data was analyzed by Analysis of Variace (ANOVA) using F-test to know effect of treatment. If there is significantly affected by treatment continued by Multiple Range Test by Duncan (Srigandono, 1989). The experiment result shown that feed consumption, body weight gain, last body weight, carcass weight and carcass percentage significantly (P<0.05) increase, will feed conversion ratio significantly (P<0.05) decrease by tofu by-product fermented with “oncom’ yeast in the ration. The experiment result can be concluded that tofu by-product fermented with “oncom” yeast was effective as a feedstuff of broiler chicks until 20% in the rations. (Animal Production 8(2): 108-114 (2006) Key Words : Tofu by-product fermented by “oncom” yeast, performance, broiler chick
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