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Registros recuperados: 8
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Bayesian Estimation of The Impacts of Food Safety Information on Household Demand for Meat and Poultry AgEcon
Taylor, Mykel R.; Phaneuf, Daniel J..
Consumer reaction to changes in the amount of food safety information on beef, pork, and poultry available in the media is the focus of this study. Specifically, any differences in consumer reactions due to heterogeneous household characteristics are investigated. The data used in this study are monthly data from the Nielsen Homescan panel and cover the time period January 1998 to December 2005. These panel data contain information on household purchases of fresh meat and poultry as well as demographic characteristics of the participating households. The data used to describe food safety information were obtained from searches of newspapers using the Lexis-Nexis academic search engine. Consumer reactions are modeled in this study using a demand system that...
Tipo: Conference Paper or Presentation Palavras-chave: Food safety; Panel data; Gibbs sampler; Component error; Agricultural and Food Policy; Consumer/Household Economics; Food Consumption/Nutrition/Food Safety.
Ano: 2009 URL: http://purl.umn.edu/49214
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Blind submarine seismic deconvolution for long source wavelets ArchiMer
Nsiri, Benayad; Chonavel, Thierry; Boucher, Jean; Nouze, Herve.
In seismic deconvolution, blind approaches must be considered in situations where reflectivity sequence, source wavelet signal, and noise power level are unknown. In the presence of long source wavelets, strong interference among the reflectors contributions makes the wavelet estimation and deconvolution more complicated. In this paper, we solve this problem in a two-step approach. First, we estimate a moving average (MA) truncated version of the wavelet by means of a stochastic expectation-maximization (SEM) algorithm. Then, we use Prony's method to improve the wavelet estimation accuracy by fitting an autoregressive moving average (ARMA) model with the initial truncated wavelet. Moreover, a solution to the wavelet initialization problem in the SEM...
Tipo: Text Palavras-chave: Bernoulli Gaussian BG process; Blind deconvolution; Gibbs sampler; Maximum likelihood ML; Maximum posterior mode MPM; Monte Carlo Markov chains MCMCs methods; Prony algorithm; Seismic deconvolution; Stochastic expectation maximization SEM.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/00000/11030/8978.pdf
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Estimating Non-linear Weather Impacts on Corn Yield—A Bayesian Approach AgEcon
Yu, Tian; Babcock, Bruce A..
We estimate impacts of rainfall and temperature on corn yields by fitting a linear spline model with endogenous thresholds. Using Gibbs sampling and the Metropolis - Hastings algorithm, we simultaneously estimate the thresholds and other model parameters. A hierarchical structure is applied to capture county-specific factors determining corn yields. Results indicate that impacts of both rainfall and temperature are nonlinear and asymmetric in most states. Yield is concave in both weather variables. Corn yield decreases significantly when temperature increases beyond a certain threshold, and when the amount of rainfall decreases below a certain threshold. Flooding is another source of yield loss in some states. A moderate amount of heat is beneficial to...
Tipo: Working or Discussion Paper Palavras-chave: Bayesian estimation; Gibbs sampler; Hierarchical structure; Metropolis-Hastings algorithm; Non-linear; Crop Production/Industries; Production Economics; Risk and Uncertainty.
Ano: 2011 URL: http://purl.umn.edu/103915
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Genetic parameters for milk yield, lactation length and calving intervals of Murrah buffaloes from Brazil R. Bras. Zootec.
Malhado,Carlos Henrique Mendes; Malhado,Ana Claudia Mendes; Ramos,Alcides de Amorim; Carneiro,Paulo Luiz Souza; Souza,Julio César de; Pala,Akin.
The major objective of this study was to estimate heritability and genetic correlations between milk yield (MY) and calving interval (CI) and lactation length (LL) in Murrah buffaloes using Bayesian inference. The database used belongs to the genetic improvement program of four buffalo herds from Brazil. To obtain the estimates of variance and covariance, bivariate analyses were performed with the Gibbs sampler, using the program MTGSAM. The heritability coefficient estimates were 0.28, 0.03 and 0.15 for MY, CI and LL, respectively. The genetic correlations between MY and LL was moderate (0.48). However, the genetic correlation between MY and CI showed large HPD regions (highest posterior density interval). Milk yield was the only trait with clear...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Genetic correlation; Gibbs sampler; Heritability.
Ano: 2013 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-35982013000800005
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Measuring Liquidity Costs in Agricultural Futures Markets AgEcon
Frank, Julieta; Garcia, Philip.
Estimation of liquidity costs in agricultural futures markets is challenging because bid-ask spreads are usually not observed. Spread estimators that use transaction data are available, but little agreement exists on their relative accuracy and performance. We evaluate four conventional and a recently proposed Bayesian estimators using simulated data based on Roll’s standard liquidity cost model. The Bayesian estimator tracks Roll’s model relatively well except when the level of noise in the market is large. We derive an improved estimator that seems to have a higher performance even under high levels of noise which is common in agricultural futures markets. We also compute liquidity costs using data for hogs and cattle futures contracts trading on the...
Tipo: Conference Paper or Presentation Palavras-chave: Liquidity costs; Bid-ask spread; Bayesian estimation; Gibbs sampler.
Ano: 2007 URL: http://purl.umn.edu/37572
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Modelos lineales generalizados con restricciones lineales en los parámetros de regresión Colegio de Postgraduados
Colorado Martínez, Luis.
Para analizar Modelos Lineales Generalizados (MLG) con parámetro de escala conocido, en el que el vector de coeficientes de regresión se encuentra sujeto a restricciones lineales de desigualdad, en este trabajo se propone un método Bayesiano, denominado Gibbs Transfor- mado con Muestreo de Impor tancia (GTMI). Primero se implementa una cadena de Markov de Monte Carlo (MCMC) a una aproximación normal (truncada) de la distribución final del vector de coeficientes de regresión y luego se utiliza el método de importancia de muestreo, sugerido por Fosdick (1963) y Hastings (1970) para realizar inferencias en los parámetros de regresión. Para muestrear la aproximación normal truncada se propone utilizar el muestreo Gibbs eficiente propuesto por Rodríguez-Yam...
Tipo: Tesis Palavras-chave: Modelos lineales generalizados; Restricciones lineales de desigualdad; Distribución normal multivariada truncada; Muestreo Gibbs; Aproximación normal; Muestreo de importancia; Maestría; Estadística; Generalized linear models; Inequality linear constraints; Truncated multivariate normal distribution; Gibbs sampler; Importance sampling.
Ano: 2008 URL: http://hdl.handle.net/10521/1381
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Modelos lineales generalizados con restricciones lineales en los parámetros de regresión Colegio de Postgraduados
Colorado Martínez, Luis.
Para analizar Modelos Lineales Generalizados (MLG) con par ´ ametro de escala conocido, en el que el vector de coeficientes de regresi ´ on se encuentra sujeto a restricciones lineales de desigualdad, en este trabajo se propone un m ´ etodo Bayesiano, denominado Gibbs Transfor- mado con Muestreo de Impor tancia (GTMI). Primero se implementa una cadena de Markov de Monte Carlo (MCMC) a una aproximaci ´ on normal (truncada) de la distribuci ´ on final del vector de coeficientes de regresi ´ on y luego se utiliza el m ´ etodo de impor tancia de muestreo, sugerido por Fosdick (1963) y Hastings (1970) para realizar inferencias en los par ´ ametros de regresi ´ on. Para muestrear la aproximaci ´ on normal truncada se propone utilizar el muestreo...
Tipo: Tesis Palavras-chave: Modelos lineales generalizados; Restricciones lineales de desigualdad; Distribució normal multivariada truncada; Muestreo Gibbs; Aproximación normal; Muestreo de importancia Generalized linear models; Inequality linear constraints; Truncated multivariate normal distribution; Gibbs sampler; Impor tance sampling.
Ano: 2012 URL: http://hdl.handle.net/10521/1053
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Testing Day’s Conjecture that More Nitrogen Decreases Crop Yield Skewness AgEcon
Du, Xiaodong; Hennessy, David A.; Yu, Cindy L..
While controversy surrounds skewness attributes of typical yield distributions, a better understanding is important for agricultural policy assessment and for crop insurance rate setting. Day (1965) conjectured that crop yield skewness declines with an increase in low levels of nitrogen use, but higher levels have no effect. In a theoretical model based on the law of the minimum (von Liebig) technology, we find conditions under which Day’s conjecture applies. Employing four experimental plot datasets, we investigate the conjecture by introducing (a) a flexible Bayesian extension of the Just-Pope technology to incorporate skewness, and (b) a quantile-based measure of skewness shift. For corn yields, the Bayesian estimation provides strong evidence in favor...
Tipo: Working or Discussion Paper Palavras-chave: Crop insurance; Gibbs sampler; Just and Pope technology; Negative skewness; Quantile regression.; Crop Production/Industries; Political Economy; Research Methods/ Statistical Methods; Risk and Uncertainty.
Ano: 2010 URL: http://purl.umn.edu/93471
Registros recuperados: 8
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