SABIIA - Sistema Aberto e Integrado de Informação em Agricultura (Sabiia)

Thibbotuwawa, Manoj; Mugera, Amin W.; White, Benedict.

This article investigates the production efficiency of rice farming in Sri Lanka using cross section survey data of 90 farms. Past studies on rice farming have mostly focused on technical efficiency (TE). Here, we examine technical efficiency, allocative efficiency (AE) and cost efficiency (CE) using the data envelopment analysis (DEA) approach. On average, the farms were 87% technically efficient; irrigated farms were more efficient (88%) than rain-fed farms (82%). Average cost, allocative and scale efficiencies were 73%, 84% and 87%. Bias corrected TE estimate suggests an expected output expansion of 25% with a given input combination in order to become fully efficient as opposed to 16% based on the original estimates. In addition, a second stage Tobit...

Tipo: Presentation

Palavras-chave: Technical efficiency; Cost efficiency; Bootstrap; Rice farming; Sri Lanka; Crop Production/Industries.

Ano: 2012

URL: http://purl.umn.edu/124423

A two-stage productivity analysis using bootstrapped Malmquist index and quantile regression

Kaditi, Eleni A.; Nitsi, Elisavet I..

This paper examines the effects of farm characteristics and government policies in enhancing productivity growth for a sample of Greek farms, using a two-stage procedure. In the 1st-stage, non-parametric estimates of Malmquist index and its decompositions are computed, while a bootstrapping procedure is applied to provide their statistical precision. In the 2nd-stage, the productivity growth estimates are regressed on various covariates using a bootstrapped quantile regression approach. The effect that the covariates exert on productivity growth of the average producer is analyzed, as well as the marginal effect of a given covariate for individuals at different points in the conditional productivity distribution. The results indicate that there exists...

Algunos aspectos de inferencia estadística en la distribución normal asimétrica

Palavras-chave: Malmquist productivity index; Quantile regression; Bootstrap; Research Methods/ Statistical Methods; C14; C21; D24.

Ano: 2009

URL: http://purl.umn.edu/52845

Colegio de Postgraduados

Pérez Rodríguez, Paulino.

En este escrito se tratan algunos aspectos relacionados con inferencia estadística en la distribución normal asimétrica. El trabajo puede ser dividido en dos grandes apartados. El primer apartado aborda el problema de estimacióon en esta familia de distribuciones desde el punto de vista bayesiano, se muestra además cómo extender la metodología de estimación propuesta a modelos de regresión, con errores con distribución normal asimétrica. Con la ﬁnalidad de ilustrar la aplicabilidad de la metodología propuesta se presentan algunos ejemplos que se resuelven empleando el algoritmo de Metropolis, cuyo código se presenta en los apéndices. Se explora también una nueva técnica de Cadenas de Markov Monte Carlo denominada algoritmo “t-walk”que también permite...

Tipo: Tesis

Palavras-chave: Algoritmo de Metropolis; Algoritmo “t-walk”; Pruebas de hipótesis; Bootstrap; Algoritmo EM; Estadística señal-ruido; Metropolis algorithm; “T-walk” algorithm; Hypothesis tests; Bootstrap; EM algorithm; Signal noise-statistic.

Ano: 2008

URL: http://hdl.handle.net/10521/1330

Algunos Aspectos de Inferencia Estadística en la Distribución Normal Asimétrica

Colegio de Postgraduados

Pérez Rodríguez, Paulino.

En este escrito se tratan algunos aspectos relacionados con inferencia estad´ıstica en la distribuci´ on normal asim´etrica. El traba jo puede ser dividido en dos grandes apar- tados. El primer apartado aborda el problema de estimaci´ on en esta familia de dis- tribuciones desde el punto de vista bayesiano, se muestra adem´ as c´omo extender la metodolog´ıa de estimaci´on propuesta a modelos de regresi´on, con errores con distribu- ci´ on normal asim´etrica. Con la ﬁnalidad de ilustrar la aplicabilidad de la metodolog´ıa propuesta se presentan algunos ejemplos que se resuelven empleando el algoritmo de Metropolis, cuyo c´ odigo se presenta en los ap´endices. Se explora tambi´en una nue- va t´ecnica de Cadenas de Markov Monte Carlo denominada...

Tipo: Tesis

Palavras-chave: Algoritmo de Metropolis; Algoritmo “t-walk”; Pruebas de hipótesis; Bootstrap; Algoritmo EM; Estad´ıstica señal-ruido Metropolis algorithm; “t-walk” algorithm; Hypothesis tests; Bootstrap; EM algorithm; Signal noise-statistic.

Ano: 2012

URL: http://hdl.handle.net/10521/1062

Alternativas para o teste t com variâncias heterogêneas avaliadas por meio de simulação

Ciência e Agrotecnologia

Silva,Roberta Bessa Veloso; Ferreira,Daniel Furtado.

Conduziu-se este trabalho com o objetivo de avaliar os riscos de se tomar decisões erradas (erro tipo I e erro tipo II), com o aumento da diferença entre as variâncias populacionais, por meio de simulação computacional, utilizando-se o teste t de Student com o número de graus de liberdade sendo aproximado pelas alternativas de Satterthwaite (1946), valor mínimo υ = min (n1 - 1, n2 - 1) e pelo método de bootstrap. Duas populações foram geradas, e a variância da população 1 foi igual a um (σ21), e a da população 2 foi especificada em função da razão σ22/σ21, a qual assume os valores 1, 2, 8 e 16. Usando essas abordagens diferentes para o teste t, avaliaram-se as taxas de erro tipo I e tipo II. Todos os critérios controlaram adequadamente a taxa de erro tipo...

An application of the two-stage, semi-parametric approach with double bootstrap to analyze technical efficiency of Critical Access Hospitals

Palavras-chave: Erros tipo I e tipo II; Monte Carlo; Bootstrap.

Ano: 2003

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1413-70542003000100023

Nedelea, I. Cristian; Fannin, James Matthew.

This study examines technical efficiency of Critical Access Hospitals (CAH) using a two-stage approach and bootstrap procedures for making valid inference about the impact of environmental variables on CAH efficiency. In the first stage, a data envelopment analysis (DEA) efficiency estimator is used to estimate technical efficiency of each hospital in the sample. In the second stage, efficiency scores are regressed on environmental variables using a truncated regression with bootstrap. Alternatively, a double bootstrap procedure is used, where bias-corrected DEA efficiency scores, obtained by means of bootstrap in the first stage, are used in the second stage bootstrapped truncated regression. While both procedures provide valid inference in the second...

AN INDEX TO EVALUATE THE ACCEPTANCE OF SPECIALTY COFFEES IN CONSUMER GROUPS

Palavras-chave: Critical Access Hospitals; Efficiency; Two-stage approach; Bootstrap; Health Economics and Policy.

Ano: 2011

URL: http://purl.umn.edu/103606

REA

Resende,Mariana; Cirillo,Marcelo Â.; Borém,Flávio M..

ABSTRACT Numerous factors are related to the individual sensory perception of consumers, which makes it impossible to adapt a model that explains their behavior. In this context and given the scarcity of statistical indexes that evaluate preferences for specialty coffees, new statistical methods should be studied. To this end, our study aimed to create an index that measures the acceptance of specialty coffees. The index was built considering the fit of regression models as a function of principal component scores. Validation was done by significance tests, whose probabilities were obtained by bootstrapping, considering the main measures used in diagnosing outliers as weights, with application to real data from different consumer groups. The coffee...

Analysis of farm household technical efficiency in Northern Ghana using bootstrap DEA

Palavras-chave: Models; Quality; Bootstrap; Acaia; Bourbon.

Ano: 2020

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000500624

Abatania, Luke N.; Hailu, Atakelty; Mugera, Amin W..

Crop production is the main source of livelihood for households in Northern Ghana. The government is committed to improving crop production and knowledge about the technical efficiency of crop farms is essential in guiding policy decisions. This paper examined the technical efficiency of 189 crop farms in Northern Ghana using data envelopment analysis (DEA) with bootstrapping. We found that bias-corrected average technical efficiency of the sample farms is 77.26%. The estimated scale efficiency is 94.21%. In a second stage regression, we found that hired labour, geographical location of farms, gender and age of head of household significantly affect technical efficiency. Policy implications of the results are discussed.

Tipo: Presentation

Palavras-chave: Technical efficiency; DEA; Bootstrap; Ghana; OLS regression.; Farm Management.

Ano: 2012

URL: http://purl.umn.edu/124211

Analytical quality in environmental studies: uncertainty evaluation of chemical concentrations determined by INAA

BABT

França,Elvis Joacir de; Fernandes,Elisabete A. De Nadai; Bacchi,Márcio Arruda; Saiki,Mitiko.

Instrumental neutron activation analysis (INAA) is a measurement technique of high metrological level for the determination of chemical elements. In the context of BIOTA/FAPESP Program, leaves of trees have been evaluated by INAA for biomonitoring purposes of the Atlantic Forest. To assure the comparability of results in environmental studies, a leaf sample of Marlierea tomentosa (Myrtaceae family) showing the lowest concentrations of chemical elements was selected for the evaluation of analytical quality of the determination under unfavorable conditions. Nevertheless, the homogeneity of chemical concentrations of sample at the 95% of confidence level has been achieved and INAA has presented repeatability of 2% for the determination of Br, Co, Cs, Fe, K,...

Analyzing Differences in Rural Hospital Efficiency: A Data Envelopment Analysis Approach

Palavras-chave: Uncertainty; INAA; Jackknife; Bootstrap.

Ano: 2006

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132006000200016

Nedelea, I. Cristian; Fannin, James Matthew; Barnes, James N..

This study analyzes difference in efficiency among the U.S. rural hospitals using a two-stage, semi-parametric approach. Data Envelopment Analysis is used in the first stage to calculate cost, technical and allocative efficiencies of Critical Access Hospitals (CAH) and non-CAH rural hospitals. Following Simar and Wilson (2007), bootstrapped truncated regressions are used in the second stage to infer on relationship between the cost, technical and allocative inefficiencies of hospitals and some environmental variables. The estimated results show that CAHs are less cost, technical and allocative efficient than non-CAH rural hospitals. The results also show that Medicare cost-based reimbursement for CAHs has a negative effect on the efficiency of these...

Autologistic model with an application to the citrus "sudden death" disease

Palavras-chave: Efficiency; Two-stage; Semi-parametric; Bootstrap; Data envelopment analysis; Health Economics and Policy; I12; I18.

Ano: 2010

URL: http://purl.umn.edu/61391

Scientia Agricola

Krainski,Elias Teixeira; Ribeiro Junior,Paulo Justiniano; Bassanezi,Renato Beozzo; Franciscon,Luziane.

The citrus sudden death (CSD) disease affects dramatically citrus trees causing a progressive plant decline and death. The disease has been identified in the late 90's in the main citrus production area of Brazil and since then there are efforts to understand the etiology as well as the mechanisms its spreading. One relevant aspect of such studies is to investigate spatial patterns of the occurrence within a field. Methods for determining whether the spatial pattern is aggregated or not has been frequently used. However it is possible to further explore and describe the data by means of adopting an explicit model to discriminate and quantify effects by attaching parameters to covariates which represent aspects of interest to be investigated. One...

Bootstrapping a conditional moments test for normality after tobit estimation

Palavras-chave: Spatial statistics; Plant disease; Binary response variable; Pseudolikelihood; Bootstrap.

Ano: 2008

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162008000500014

Comparação de matrizes de covariâncias de populações normais dependentes: um estudo de caso

Drukker, David M..

Categorical and limited dependent variable models are routinely estimated via maximum likelihood. It is well-known that the ML estimates of the parameters are inconsistent if the distribution or the skedastic component is misspecified. When conditional moment tests were first developed by Newey (1985) and Tauchen (1985), they appeared to offer a wide range of easy-to-compute specification tests for categorical and limited dependent variable models estimated by maximum likelihood. However, subsequent studies found that using the asymptotic critical values produced severe size distortions. This paper presents simulation evidence that the standard conditional moment test for normality after tobit estimation has essentially no size distortion and reasonable...

Tipo: Journal Article

Palavras-chave: Conditional moment tests; Bootstrap; Tobit; Normality; Research Methods/ Statistical Methods.

Ano: 2002

URL: http://purl.umn.edu/115956

Ciência e Agrotecnologia

Cirillo,Marcelo Angelo; Ferreira,Daniel Furtado; Sáfadi,Thelma.

Inferências sobre comparações de matrizes de covariâncias em populações normais dependentes são usualmente obtidas considerando testes assintóticos baseados na maximização de funções de verossimilhanças. Entretanto, se o número de populações e/ou de variáveis consideradas é excessivo pode-se ter problemas na convergência dos métodos numéricos utilizados para obtenção dos estimadores de máxima verossimilhança. Face a esse problema, objetivou-se, neste trabalho, ilustrar por meio de um conjunto de dados reais, a aplicação de um teste para comparar matrizes de covariâncias de populações correlacionadas, usando uma estatística baseada na razão de variâncias generalizadas, cuja distribuição empírica foi obtida por meio da técnica bootstrap.

Comparación de estimadores para volumen maderable en selva mediana del sureste de México

Palavras-chave: Bootstrap; Covariâncias; Variâncias generalizadas.

Ano: 2009

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1413-70542009000700015

Agrociencia

Velasco-Bautista,Efraín; Santos-Posadas,Héctor de los; Ramírez-Maldonado,Hugo; Rendón-Sánchez,Gilberto.

Resumen En México, el proyecto Inventario Nacional Forestal y de Suelos (INFyS) utiliza para el análisis estadístico de los datos dasométricos estimadores de razón cuya aplicación es fácil. Sin embargo, en circunstancias diversas podría ser imposible obtener datos que cumplan por completo con sus supuestos teóricos. En este estudio se compararon los resultados del estimador de razón del INFyS con estimadores alternativos. Con datos del 2010 provenientes de la malla de muestreo obtenida en selva mediana subperennifolia y subcaducifolia en Quintana Roo y Campeche, México, se compararon estadísticamente los estimadores: razón de medias, medias de razones e Inventario Forestal y Análisis (FIA-USDA). El sesgo relativo del estimador de razón (sesgo respecto al...

URL: http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-31952016000100119

Palavras-chave: Razón de medias; Media de razones; Bootstrap; Zonas de inclusión espacialmente disjuntas.

Ano: 2016

Confidence intervals for predicted outcomes in regression models for categorical outcomes

Crop Insurance, Disaster Payments and Land Use Change: The Effect of Sodsaver on Incentives for Grassland Conversion

Xu, Jun; Long, J. Scott.

We discuss methods for computing confidence intervals for predictions and discrete changes in predictions for regression models for categorical outcomes. The methods include endpoint transformation, the delta method, and bootstrapping. We also describe an update to prvalue and prgen from the SPost package, which adds the ability to compute confidence intervals. The article provides several examples that illustrate the application of these methods.

Tipo: Journal Article

Palavras-chave: Prvalue; Prgen; Confidence interval; Predicted probability; Discrete choice models; Endpoint transformation; Delta method; Bootstrap; Research Methods/ Statistical Methods.

Ano: 2005

URL: http://purl.umn.edu/117544

Claassen, Roger; Cooper, Joseph C.; Carriazo, Fernando.

Subsidized crop insurance may encourage conversion of native grassland to cropland. The Sodsaver provision of the 2008 farm bill could deny crop insurance on converted land in the Prairie Pothole states for 5 years. Supplemental Revenue Assistance payments, which are linked to crop insurance purchases, could also be withheld. Using representative farms, we estimate that Sodsaver would reduce expected crop revenue by up to 8% and expected net return by up to 20%, while increasing the standard deviation of revenue by as much as 6% of market revenue. Analysis based on elasticities from the literature suggests that Sodsaver would reduce grassland conversion by 9% or less.

Tipo: Journal Article

Palavras-chave: Bootstrap; Crop insurance; Grassland; Joint densities; Sodsaver; Supplemental Revenue Assistance; Agricultural and Food Policy; Production Economics; Risk and Uncertainty; Q2.

Ano: 2011

URL: http://purl.umn.edu/104623

Determinación de tamaño de muestra de características del xilema de brote de aguacate mediante remuestreo

PAB

Meza-Castillo,Elizabeth; Barrientos-Priego,Alejandro Facundo; Rodríguez-Pérez,Juan Enrique; Reyes-Santamaría,María Isabel.

El propósito de este trabajo fue determinar el tamaño de muestra adecuado, para detectar diferencias estadísticas en análisis de varianza de los caracteres de xilema, en brotes anuales de aguacate. Para esto, fueron registradas en tres árboles con altura contrastante las variables frecuencia, área, perímetro y diámetro de los vasos del xilema. A partir de 50 observaciones de cada árbol, se realizaron 5.000 remuestreos no paramétricos, para cada repetición de 2 a 50 campos microscópicos. A partir del tamaño de muestra de 15 repeticiones, las desviaciones en los cinco estadísticos son mínimas, por lo que se propone como el mínimo para el muestreo de dichas variables.

Tipo: Info:eu-repo/semantics/report

Palavras-chave: Persea americana; Análisis de varianza; Bootstrap; Vasos del xilema.

Ano: 2010

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-204X2010001200026

Determinants of Cost Inefficiency of Critical Access Hospitals: A Two-stage, Semi-parametric Approach

Nedelea, I. Cristian; Fannin, James Matthew.

This study examines, post-conversion, cost inefficiency of Critical Access Hospitals (CAH) using a two-stage approach. While the results suggest that Medicare cost-based reimbursement and longer participation in the CAH program may increase the cost inefficiency of CAHs, the extent of this inefficiency increase is lower than what previous literature showed.

Divergence - Is it Geography?

Palavras-chave: Critical Access Hospitals; Cost inefficiency; Two-stage approach; Bootstrap; Community/Rural/Urban Development; Health Economics and Policy; Production Economics; I18.

Ano: 2011

URL: http://purl.umn.edu/98643

Straubhaar, Thomas; Suhrcke, Marc; Urban, Dieter.

This paper tests a geography and growth model using regional data for Europe, the US, and Japan. We set up a standard geography and growth model with a poverty trap and derive a log-linearized growth equation that corresponds directly to a threshold regression technique in econometrics. In particular, we test whether regions with high population density (centers) grow faster and have a permanently higher per capita income than regions with low population density (peripheries). We find geography driven divergence for US states and European regions after 1980. Population density is superior in explaining divergence compared to initial income which the most important official EU eligibility criterium for regional aid is built on. Divergence is stronger on...

Tipo: Working or Discussion Paper

Palavras-chave: Threshold estimation; New economic geography; Regional income; Growth; Poverty trap; Regime shifts; Bootstrap; International Development; O41; R11; F12.

Ano: 2002

URL: http://purl.umn.edu/26350

Does Farm Size and Specialization Matter for Productive Efficiency? Results from Kansas