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A menu-driven facility for complex sample size calculation in randomized controlled trials with a survival or a binary outcome AgEcon
Royston, Patrick; Babiker, Abdel.
We present a menu-driven Stata program for the calculation of sample size or power for complex clinical trials with a survival time or a binary outcome. The features supported include up to six treatment arms, an arbitrary time-to-event distribution, fixed or time-varying hazard ratios, unequal patient allocation, loss to follow-up, staggered patient entry, and crossover of patients from their allocated treatment to an alternative treatment. The computations of sample size and power are based on the logrank test and are done according to the asymptotic distribution of the logrank test statistic, adjusted appropriately for the design features.
Tipo: Journal Article Palavras-chave: Randomized controlled trials; Survival analysis; Logrank test; Experimental design; Research Methods/ Statistical Methods.
Ano: 2002 URL: http://purl.umn.edu/115958
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A Software Package and Hardware Tools for in situ Experiments in a Lagrangian Reference Frame ArchiMer
Doglioli, Andrea; Nencioli, Francesco; Petrenko, Anne; Rougier, Gilles; Fuda, Jean-luc; Grima, Nicolas.
The Lagrangian Transport Experiment (LATEX) was developed to study the influence of coupled physical and biogeochemical dynamics at the meso- and submesoscales on the transfers of matter and heat between the coastal zone and the open ocean. One of the goals of the Latex10 field experiment, conducted during September 2010 in the Gulf of Lion (northwest Mediterranean), was to mark a dynamical mesoscale feature by releasing a passive tracer [sulfur hexafluoride (SF6)] together with an array of Lagrangian buoys. The goal was to release the tracer in an initial patch as homogeneous as possible in the horizontal, and to study its turbulent mixing and dispersion while minimizing the contribution due to advection. For that, it was necessary to continuously adjust...
Tipo: Text Palavras-chave: Dispersion; Lagrangian circulation; Transport; Ship observations; Tracers; Experimental design; Software.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00155/26590/24719.pdf
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Adaptive Experimental Design Using the Propensity Score AgEcon
Hahn, Jinyong; Hirano, Keisuke; Karlan, Dean S..
Many social experiments are run in multiple waves, or are replications of earlier social experiments. In principle, the sampling design can be modified in later stages or replications to allow for more efficient estimation of causal effects. We consider the design of a two-stage experiment for estimating an average treatment effect, when covariate information is available for experimental subjects. We use data from the first stage to choose a conditional treatment assignment rule for units in the second stage of the experiment. This amounts to choosing the propensity score, the conditional probability of treatment given covariates. We propose to select the propensity score to minimize the asymptotic variance bound for estimating the average treatment...
Tipo: Working or Discussion Paper Palavras-chave: Experimental design; Propensity score; Efficiency bound; Research Methods/ Statistical Methods; C1; C14; C9; C93; C13.
Ano: 2009 URL: http://purl.umn.edu/47107
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Agent-based Analysis of Agricultural Policies: an Illustration of the Agricultural Policy Simulator AgriPoliS, its Adaptation and Behavior Ecology and Society
Happe, Kathrin; Leibniz Institute of Agricultural Development in Central and Eastern Europe; happe@iamo.de; Kellermann, Konrad; Leibniz Institute of Agricultural Development in Central and Eastern Europe; kellermann@iamo.de; Balmann, Alfons; Leibniz Institute of Agricultural Development in Central and Eastern Europe; balmann@iamo.de.
This paper combines agent-based modeling of structural change with agricultural policy analysis. Using the agent-based model AgriPoliS, we investigate the impact of a regime switch in agricultural policy on structural change under various framework conditions. Instead of first doing a sensitivity analysis to analyze the properties of our model and then examining the introduced policy in an isolated manner, we use a meta-modeling approach in combination with the statistical technique of Design of Experiments to systematically analyze the relationship between policy change and model assumptions regarding key determinants of structural change such as interest rates, managerial abilities, and technical change. As a result, we observe that the effects of...
Tipo: Peer-Reviewed Reports Palavras-chave: Agent-based modeling; Agricultural policy analysis; Empirical-based simulation; Experimental design; Farm structures; Meta-modeling..
Ano: 2006
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An Assessment of the Precision and Confidence of Aquatic Eddy Correlation Measurements ArchiMer
Donis, Daphne; Holtappels, Moritz; Noss, Christian; Cathalot, Cecile; Hancke, Kasper; Polsenaere, Pierre; Wenzhoefer, Frank; Lorke, Andreas; Meysman, Filip J. R.; Glud, Ronnie N.; Mcginnis, Daniel F..
The quantification of benthic fluxes with the aquatic eddy correlation (EC) technique is based on simultaneous measurement of the current velocity and a targeted bottom water parameter (e.g., O2, temperature). High-frequency measurements (64 Hz) are performed at a single point above the seafloor using an acoustic Doppler velocimeter (ADV) and a fast-responding sensor. The advantages of aquatic EC technique are that 1) it is noninvasive, 2) it integrates fluxes over a large area, and 3) it accounts for in situ hydrodynamics. The aquatic EC has gained acceptance as a powerful technique; however, an accurate assessment of the errors introduced by the spatial alignment of velocity and water constituent measurements and by their different response times is...
Tipo: Text Palavras-chave: Turbulence; Boundary layer; Fluxes; Instrumentation/sensors; Optimization; Experimental design.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00275/38577/37102.pdf
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Analise de experimentos em latice quadrado com enfase em componentes de variancia. I. Analises individuais. Repositório Alice
SILVA, H.D.; REGAZZI, A.J.; CRUZ, C.D.; VIANA, J.M.S..
Este trabalho teve como objetivo avaliar as seguintes alternativas de anlise de experimentos em latice quadrado ("Square Lattice"), quanto a estimacao de componentes de variancia e alguns parametros geneticos: i) analise intrablocos com tratamentos ajustados, e blocos dentro de repeticoes nao-ajustados; ii) analise do latice como blocos casualizados completos; iii) analise intrablocos com tratamentos nao-ajustados e blocos dentro de repeticoes ajustados; iv) analise do latice como blocos casualizados completos, utilizando-se as medidas ajustadas dos tratamentos, obtidas a partir da analise com recuperacao da informacao interblocos, tendo como quadrado medio do residuo a variancia efetiva media desta mesma analise com recuperacao da informacao interblocos....
Tipo: Artigo em periódico indexado (ALICE) Palavras-chave: Delineamento experimentais; Parametros geneticos; Melhoramento de plantas; Experimental design; Genitic parameters; Plant breeding.
Ano: 1999 URL: http://www.alice.cnptia.embrapa.br/handle/doc/101025
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Analysis of experiments in square lattice with emphasis on variance components. i. Individual analysis PAB
Silva,Heyder Diniz; Regazzi,Adair José; Cruz,Cosme Damião; Viana,José Marcelo Soriano.
This paper focused on four alternatives of analysis of experiments in square lattice as far as the estimation of variance components and some genetic parameters are concerned: 1) intra-block analysis with adjusted treatment and blocks within unadjusted repetitions; 2) lattice analysis as complete randomized blocks; 3) intrablock analysis with unadjusted treatment and blocks within adjusted repetitions; 4) lattice analysis as complete randomized blocks, by utilizing the adjusted means of treatments, obtained from the analysis with recovery of interblock information, having as mean square of the error the mean effective variance of this same analysis with recovery of inter-block information. For the four alternatives of analysis, the estimators and estimates...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Experimental design; Genetic parameters; Plant breeding.
Ano: 1999 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-204X1999001000007
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Assessment of oxidation of leaves of Ilex paraguariensis (St. Hil) BABT
Molin,Rochele Fernanda; Valduga,Alice Teresa; Di Luccio,Marco; Dartora,Nessana; Cichoski,Alexandre José; Pistore,Mônica; Rigo,Elisandra.
This work aimed to study the oxidation of leaves of Ilex paraguariensis St. Hil, in a process similar to the oxidation of Camellia sinensis, with the purpose of developing new products based on yerba maté. So far, no previous systematic study about the oxidation of yerba maté has been found elsewhere. A Plackett-Burman experimental design was used for the screening of the significant parameters that affected the oxidation. The oxidation was indirectly quantified by following the changes in the product color, water activity, and pH with the time of processing. The factors that most influenced the process were the age of the leaves and the relative humidity of the oxidation chamber. The differences between the treatments were more evident after 3, 6 12 and...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Physicochemical parameters; Yerba maté; Leave; Extract; Experimental design.
Ano: 2011 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132011000200016
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Chiral discrimination of amlodipine from pharmaceutical products using capillary electrophoresis BJPS
Cârcu-Dobrin,Melania; Sabău,Alexandra Georgiana; Hancu,Gabriel; Árpád,Gyéresi; Rusu,Aura; Kelemen,Hajnal; Papp,Lajos Attila; Cârje,Anca.
The present work describes the development of a capillary electrophoresis (CE) method for the chiral discrimination of amlodipine (AML) enantiomers using cyclodextrine (CD) derivatives as chiral selectors. A large number of native and derivatized, neutral and ionized CD derivatives were screened to find the optimal chiral selector; and carboximethyl-β-CD (CM-β-CD) was selected for the enantiomeric discrimination. A factorial analysis study was performed by orthogonal experimental design in which several factors were varied at the same time to optimize the separation method. The optimized method (25 mM phosphate buffer, pH = 9.0, 15 mM CM-β-CD, 15 ºC, + 25 kV, 30 mbar/1 second, detection wavelength 230 nm) was successfully applied for the baseline...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Amlodipine; Capillary electrophoresis; Chiral separation; Cyclodextrine; Experimental design.
Ano: 2020 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-82502020000100530
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Coeficiente de heterogeneidade do solo e tamanho de parcela. Repositório Alice
ALVES, S.M. de F.; SERAPHIN, J.C..
O objetivo deste trabalho foi apresentar alternativas para estimar o coeficiente de heterogeneidade do solo a partir do coeficiente de correlação intraclasse em diferentes estruturas de delineamentos experimentais. As estimativas dos coeficientes de heterogeneidade do solo obtidas por este método foram comparadas àquelas obtidas por meio de mínimos quadrados generalizados. Não houve diferenças entre as estimativas obtidas por ambos os métodos; nesse caso recomenda-se a estimativa com base no coeficiente de correlação intraclasse por ser mais simples e prática. Considerando-se o coeficiente de heterogeneidade do solo, obteve-se diversos tamanhos de parcela, para diferentes combinações de coeficiente de variação, número de repetições, grau de diferença que...
Tipo: Artigo em periódico indexado (ALICE) Palavras-chave: Coeficiente de correlação intraclasse; Precisão experimental; Delineamento experimental; Coeficiente de variação; Intraclass correlation coefficient; Experimental precision; Experimental design; Variation coefficient.
Ano: 2004 URL: http://www.alice.cnptia.embrapa.br/handle/doc/110071
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Comparison of analyses types in carrot experiment: square lattice versus randomized blocks design Horticultura Brasileira
Carvalho,Agnaldo DF; Silva,Giovani O.
ABSTRACT The square lattice 4x4 design was compared to a randomized block design, for carrot F1 hybrids. Sixteen experimental carrot hybrids were evaluated in Brasília, in 2014/15 and 2015/16 agricultural years. A square lattice 4x4 design with three replications was used. The experimental plot consisted of 1.5 m2 useful area. The experimental area was installed on the second half of November 2014 and 2015. Cultural practices were the usually given to the carrot crop in Brazilian savannah region. The incidence of leaf blight was evaluated 90 days after sowing date and, after 100 days, roots were harvested and yield components evaluated. We evaluated the three possible analyses in lattice: 1) as randomized block design; 2) intrablock analysis with adjusted...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Daucus carota; Experimental design; Incomplete block.
Ano: 2018 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0102-05362018000200217
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Development of a generic method for the determination of proton-pump inhibitors by capillary zoneelectrophoresis BJPS
Papp,Lajos Attila; Gyéresi,Árpád; Hancu,Gabriel; Mircia,Eleonora; Kelemen,Hajnal.
A generic capillary zone electrophoresis method was developed for the analysis of four proton pump inhibitors: omeprazole, pantoprazole, lansoprazole and rabeprazole. During preliminary analysis screening of phosphate buffers at different pH levels was performed, in order to determine the optimum pH domain suitable for the simultaneous determination of all studied compounds. A face centered central composite design was employed for the optimization of separation conditions. The effect of buffer concentration, pH and applied voltage was studied; resolution between peaks and migration time of the last compound were considered as responses. Other factors as system temperature, injection parameters, capillary length, were held constant during the optimization...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Capillary electrophoresis; Proton-pump inhibitors; Experimental design.
Ano: 2019 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-82502019000100534
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Do different sampling designs produce differences in the metrics of curimba, Prochilodus lineatus (Characiformes: Prochilodontidae)? Neotropical Ichthyology
Kurchevski,Gregório; Godinho,Alexandre Lima.
ABSTRACT Probabilistic sampling, a classical recommendation for unbiased data, has been often overlooked. Fish sampling in reservoirs, unlike most rivers, can be accomplished by a variety of probabilistic sampling designs due to few restrictions in the choice of sampling sites (SSs). We evaluated whether population metrics of Prochilodus lineatus differ between fixed SSs (do not change with each sampling trip) and variable SSs (change with each sampling trip) in the Volta Grande (VGR) and Jaguara (JR) reservoirs of the Grande River, Paraná River basin, Brazil. We used gillnets to sample fish at nine probabilistic fixed SSs and nine probabilistic variable SSs per sampling trip. We conducted 25 sampling trips in VGR and 22 in JR during 2011 to 2015, and...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Experimental design; Fixed versus variable sampling sites; Grande River basin; Probabilistic sampling; Reservoir.
Ano: 2018 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252018000400216
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Effect of ultrasound on the quality parameters of a banana, strawberry and juçara juice blend. Repositório Alice
RIBEIRO, L. O.; BRIGIDA, A. I. S.; MATTA, V. M. da; FREITAS, S. P..
In this study, the effect of ultrasound processing on the quality parameters of a banana, strawberry and juçara juice blend was evaluated. A central composite rotational design was performed in which the processing power (73.5 to 250 Watts) and time (7 to 36 minutes) were selected as independent variables. The blend was sonicated and then pH, acidity, soluble solids and anthocyanins were evaluated as experimental design responses. It was observed anthocyanins retention of at least 86% in the sonicated fruit juice blends and there was no significant variation in pH, titrable acidity and soluble solids content. Therefore, the ultrasound may become a potential technology for fruit juice blends stabilization.
Tipo: Artigo em anais de congresso (ALICE) Palavras-chave: Ultrasound; Experimental design; Physical-chemical characteristics.
Ano: 2016 URL: http://www.alice.cnptia.embrapa.br/handle/doc/1057303
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Efficiency benefits of choice model experimental design updating: a case study AgEcon
Kerr, Geoffrey N.; Sharp, Basil M.H..
Efficient experimental designs offer the potential to reduce confidence intervals for parameters of interest in choice models, or to reduce required sample sizes. C-efficiency recognises the salience of willingness to pay estimates rather than utility function parameters. This study reports on a choice model application that incorporated updated statistical designs based on initial responses in order to maximise C-efficiency. The revised design delivered significant improvements.
Tipo: Conference Paper or Presentation Palavras-chave: Experimental design; Choice experiment; Efficiency; Research Methods/ Statistical Methods.
Ano: 2009 URL: http://purl.umn.edu/47623
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Efficient design for willingness to pay in choice experiments: evidence from the field AgEcon
Kerr, Geoffrey N.; Sharp, Basil M.H..
Efficient experimental designs offer the potential to reduce confidence intervals for parameters of interest in choice models, or to reduce required sample sizes. C-efficiency recognizes the salience of willingness to pay estimates rather than utility function parameters. This study reports on a choice model application that incorporated updated statistical designs based on initial responses in order to maximize C-efficiency. The revised design delivered significant improvements.
Tipo: Conference Paper or Presentation Palavras-chave: Experimental design; Choice experiment; Efficiency; Environmental Economics and Policy; Research Methods/ Statistical Methods.
Ano: 2009 URL: http://purl.umn.edu/97156
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Estimating variance components in Stata AgEcon
Marchenko, Yulia V..
This article gives a brief overview of the popular methods for estimating variance components in linear models and describes several ways to obtain such estimates in Stata for various experimental designs. The article’s emphasis is on using xtmixed to estimate variance components. Prior to Stata 9, loneway could be used to estimate variance components for one-way random-effects models. For other experimental designs, variance components could be computed manually using saved results after anova. The latter approach is viable but requires tedious computations for complicated experimental designs. Instead, as of Stata 9, variance components are easily obtained by using xtmixed.
Tipo: Journal Article Palavras-chave: Variance components; Experimental design; ANOVA; REML; ML; Multilevel; Random coefficients; Mixed models; Research Methods/ Statistical Methods.
Ano: 2005 URL: http://purl.umn.edu/117553
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Estudo do arranjo espacial de plantas da cultura do arroz de terras altas em Mato Grosso do Sul. Repositório Alice
BAZONI, R.; FERNANDES, A. T. F.; COSTA, C. A.; GUIMARÃES, E. P.; CARVALHO, J. R. P. de; SANTOS, A. B. dos..
Na década de 70, com advento do programa de financiamentos agropecuários "Polocentro", a cultura de arroz de terras altas tomou grande impulso, especialmente no cerrado do Brasil Central, quando essa região tornou-se responsável pela maior área de cultivo nesse sistema.
Tipo: Artigo em anais de congresso (ALICE) Palavras-chave: Arroz; Oryza sativa; Delineamento experimental; Estatistica experimental; Densidade e espaçamento de arroz; Experimental design; Experimental statistics; Rice density and spacing.
Ano: 1998 URL: http://www.alice.cnptia.embrapa.br/alice/handle/doc/206422
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Evaluation of process parameters in the industrial scale production of fish nuggets Ciênc. Tecnol. Aliment.
Silva,Adriane da; Zitkoski,João; Mazutti,Marcio Antônio; Mossi,Altemir; Oliveira,José Vladimir; Oliveira,Débora de; Cichoski,Alexandre José; Treichel,Helen.
This work reports the use of experimental design for the assessment of the effects of process parameters on the production of fish nuggets in an industrial scale environment. The effect of independent factors on the physicochemical and microbiological parameters was investigated through a full 24 experimental design. The studied factors included the temperature of fish fillet and pulp in the mixer, the temperature of the added fat, the temperature of water and the ratio of protein extraction time to emulsion time. The physicochemical analyses showed that the higher temperature of the pulp and fillet of fish, the lower the protein in the final product. Microbiological analyses revealed that the counting of Staphylococcus coagulase positive, total and...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Fish nuggets; Experimental design; Process parameters.
Ano: 2011 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0101-20612011000200019
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Experimental design and data analysis: methods for the response optimization and applications using R. Repositório Alice
OLIVEIRA, T. A.; LEAL, C.; LIMA, R..
2015
Tipo: Resumo em anais de congresso (ALICE) Palavras-chave: Análise de dados; Experimental design.
Ano: 2015 URL: http://www.alice.cnptia.embrapa.br/handle/doc/1007520
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