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

Proving causal relationships using observational data

Marsh, Thomas L..

We conceptualize wheat for food use as an input into flour production and derive demand functions to quantify price responsiveness and economic substitutability across wheat classes. Cost, price, and substitution elasticities are estimated for hard red winter, hard red spring, soft red wheat, soft white winter, and durum wheat. In general, hard red winter and spring wheat varieties are much more responsive to their own price than are soft wheat varieties and durum wheat. Morishima elasticities indicate that hard red winter and hard red spring wheat are economic substitutes for milling purposes.

Tipo: Conference Paper or Presentation

Palavras-chave: Elasticities; Wheat by class; Economic substitution; Monte Carlo; Food Consumption/Nutrition/Food Safety; C15; C30; Q11.

Ano: 2003

URL: http://purl.umn.edu/57920

Bryant, Henry L.; Bessler, David A..

We describe a means of rejecting a null hypothesis concerning observed, but not deliberately manipulated, variables of the form H0: A -/-> B in favor of an alternative hypothesis HA: A --> B, even given the possibility of causally related unobserved variables. Rejection of such an H0 relies on the availability of two observed and appropriately related instrumental variables. While the researcher will have limited control over the confidence level in this test, simulation results suggest that type I errors occur with a probability of less than 0.15 (often substantially less) across a wide range of circumstances. The power of the test is limited if there are but few observations available and the strength of correspondence among the variables is weak....

Tipo: Conference Paper or Presentation

Palavras-chave: Causality; Monte Carlo; Observational data; Hypothesis testing; Research Methods/ Statistical Methods.

Ano: 2011

URL: http://purl.umn.edu/103238

Economic substitution for US wheat food use by class

Shade-Grown Coffee: Simulation and Policy Analysis for Coastal Oaxaca, Mexico

Marsh, Thomas L..

Wheat for food use is conceptualised as an input into flour production and demand is derived from an industry profit function to quantify price responsiveness and economic substitutability across wheat classes. Price and substitution elasticities are estimated for hard red winter, hard red spring, soft red wheat, soft white winter and durum wheat. In general, hard red winter and spring wheat varieties are much more responsive to their own price than are soft wheat varieties and durum wheat. Substitution elasticities indicate that hard red winter and hard red spring wheat are economic substitutes for milling purposes.

Tipo: Article

Palavras-chave: Elasticities; Like product; Monte Carlo; Wheat by class; Crop Production/Industries; Food Consumption/Nutrition/Food Safety.

Ano: 2005

URL: http://purl.umn.edu/118503

Batz, Michael B.; Albers, Heidi J.; Avalos-Sartorio, Beatriz; Blackman, Allen.

Shade-grown coffee provides a livelihood to many farmers, protects biodiversity, and creates environmental services. Many shade-coffee farmers have abandoned production in recent years, however, in response to declines in international coffee prices. This paper builds a farmer decision model under price uncertainty and uses simulation analysis of that model to examine the likely impact of various policies on abandonment of shade-coffee plantations. Using information from coastal Oaxaca, Mexico, this paper examines the role of various constraints in abandonment decisions, reveals the importance of the timing of policies, and characterizes the current situation in the study region.

Tipo: Working or Discussion Paper

Palavras-chave: Coffee farming; Decision analysis; Numerical modeling; Monte Carlo; Price variability; Crop Production/Industries; O13; Q17; Q12; Q23; Q24.

Ano: 2005

URL: http://purl.umn.edu/10511

CITRICULTURE ECONOMIC AND FINANCIAL EVALUATION UNDER CONDITIONS OF UNCERTAINTY

Rev. Bras. Frutic.

SIMÕES,DANILO; CABRAL,ANTÔNIO CARLOS; OLIVEIRA,PAULO ANDRÉ DE.

ABSTRACT The citriculture consists in several environmental risks, as weather changes and pests, and also consists in considerable financial risk, mainly due to the period ofreturn on the initial investment. This study was motivated by the need to assess the risks of a business activity such as citriculture. Our objective was to build a stochastic simulation model to achieve the economic and financial analysis of an orange producer in the Midwest region of the state of Sao Paulo, under conditions of uncertainty. The parameters used were the Net Present Value (NPV), the Modified Internal Rate of Return(MIRR), and the Discounted Payback. To evaluate the risk conditions we built a probabilistic model of pseudorandom numbers generated with Monte Carlo method....

Economic optimization of the number of recipients in bovine embryo transfer programs

Palavras-chave: Risk analysis; Citrus sinensis Osbeck; Agricultural economics; Monte Carlo.

Ano: 2015

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-29452015000400859

Scientia Agricola

Beltrame,Renato Travassos; Barioni,Luis Gustavo; Maestri,Breno Dala; Quirino,Celia Raquel.

Purchase and maintenance of recipient females account for a large proportion of the costs and determine the number of calves that can be produced in an embryo transfer program. However, the large variability of embryo production by the donors and the need to purchase and synchronize the recipients before knowing the number of embryos collected make it difficult for the decision maker to identify the ideal number of recipient females to allocate. An ex-ante evaluation to determine the optimal number of recipient females was carried out through a sensitivity analysis for the ratio between the number of recipients and donors in a simulation model. The variability for the number of embryos collected was accounted for by applying the Monte Carlo simulation...

Construcción de unidades representativas de producción porcina y análisis de su viabilidad económica en el período 2009-2018

Palavras-chave: Monte Carlo; Mathematical model; Simulation; Cost estimation; Estrus synchronization.

Ano: 2007

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162007000300002

Agrociencia

Zavala-Pineda,M. Jesica; Salas-González,J. María; Leos-Rodríguez,J. Antonio; Sagarnaga-Villegas,L. Myriam.

En este estudio se destaca la relevancia de los estudios prospectivos en el diseño de una política agropecuaria diferenciada para México y en la identificación de los efectos potenciales de políticas sectoriales diferenciadas. Por tanto, el objetivo del estudio fue analizar la viabilidad económica de unidades representativas de producción (URP) porcícola en los estados de Jalisco, Sonora y Guanajuato. La técnica de paneles se usó para modelar 15 URP con la participación de 137 productores, con granjas similares en tecnología, escala, sistema de producción, ubicación geográfica y mercado de destino del producto. Mediante consensos se identificó la información técnica y financiera relevante para construir el Año Base 2008. Con esta información y empleando el...

URL: http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-31952012000700008

Palavras-chave: Análisis prospectivo; Monte Carlo; Paneles; Simulación; Transferencias gubernamentales.

Ano: 2012

ANÁLISE QUANTITATIVA DO RISCO TÉCNICO-ECONÔMICO DE UM TRATOR FLORESTAL SKIDDER

BIOFIX

Miyajima, Ricardo Hideaki; Tonin, Rodrigo Petrongari; Fenner, Paulo Torres; Simões, Danilo.

Os custos da colheita florestal, de forma abrangente, podem ser definidos como a quantificação econômica dos fatores produtivos, determinados em sua maioria pelo modal utilizado. Todavia, um elemento presente no conhecimento dos custos desses modais é a incerteza nas estimativas, devido ao conjunto de fatores envolvidos ou da insuficiência de informações. À vista disso, objetivou-se neste estudo construir um modelo estocástico, a partir da produtividade operacional de um trator florestal skidder empregado na extração de Eucalyptus sp., para quantificar os riscos técnico-econômicos por meio da simulação de Monte Carlo. A análise técnico-econômica teve como premissa o estudo de tempos e métodos, seguida da estimativa do custo horário do trator florestal...

Selecting “the best” nonstationary Generalized Extreme Value (GEV) distribution: on the influence of different numbers of GEV-models

Palavras-chave: Colheita florestal; Custos de extração; Monte Carlo; Silvicultura; Tempos e métodos.

Ano: 2017

URL: http://revistas.ufpr.br/biofix/article/view/56339

Bragantia

Xavier,Ana Carolina Freitas; Blain,Gabriel Constantino; Morais,Marcos Vinicius Bueno de; Sobierajski,Graciela da Rocha.

ABSTRACT The selection of an appropriate nonstationary Generalized Extreme Value (GEV) distribution is frequently based on methods, such as Akaike information criterion (AIC), second-order Akaike information criterion (AICc), Bayesian information criterion (BIC) and likelihood ratio test (LRT). Since these methods compare all GEV-models considered within a selection process, the hypothesis that the number of candidate GEV-models considered in such process affects its own outcomehas been proposed. Thus, this study evaluated the performance of these four selection criteria as function of sample sizes, GEV-shape parameters and different numbers candidate GEV-models. Synthetic series generated from Monte Carlo experiments and annual maximum daily rainfall...

Uncertainty of the density of moist air: Gum x Monte Carlo

Palavras-chave: Monte Carlo; GEV; MIROC5; Downscaling.

Ano: 2019

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052019000400606

BABT

Canaves Junior,Moacyr; Pompéia,Pedro José.

In this study two methods of evaluation of uncertainty, the law of propagation of uncertainties (as recommended by GUM) and the method of Monte Carlo, are compared. As a particular case the determination of the density of moist air was considered The results show that there are some differences between both methods.

Sisvar: a Guide for its Bootstrap procedures in multiple comparisons

Palavras-chave: Density of moist air; Propagation of uncertainties; Monte Carlo.

Ano: 2006

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132006000200014

Ferreira,Daniel Furtado.

Sisvar is a statistical analysis system with a large usage by the scientific community to produce statistical analyses and to produce scientific results and conclusions. The large use of the statistical procedures of Sisvar by the scientific community is due to it being accurate, precise, simple and robust. With many options of analysis, Sisvar has a not so largely used analysis that is the multiple comparison procedures using bootstrap approaches. This paper aims to review this subject and to show some advantages of using Sisvar to perform such analysis to compare treatments means. Tests like Dunnett, Tukey, Student-Newman-Keuls and Scott-Knott are performed alternatively by bootstrap methods and show greater power and better controls of experimentwise...

Comparações múltiplas bayesianas em modelos normais homocedásticos e heterocedásticos

Palavras-chave: Monte Carlo; Type I error; Power.

Ano: 2014

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1413-70542014000200001

Andrade,Paulo César de Resende; Ferreira,Daniel Furtado.

Procedimentos de comparações múltiplas são utilizados para comparar médias de níveis de um fator, porém, os testes mais populares apresentam problemas de ambiguidade dos resultados e de controle do erro tipo I, além de terem seus desempenhos influenciados negativamente no caso de heterogeneidade de variâncias e não balanceamento. Objetivou-se, neste trabalho propor alternativas bayesianas para comparações múltiplas considerando os casos de homogeneidade e heterogeneidade de variâncias. A metodologia utilizada nesse trabalho foi baseada na distribuição a posteriori t multivariada. Foram geradas k cadeias de médias, utilizando o método de Monte Carlo. Foi obtida a amplitude padronizada sob H0, obtida na distribuição a posteriori das médias, contemplando a...

Robustness of asymptotic and bootstrap tests for multivariate homogeneity of covariance matrices

Palavras-chave: Simulação; Erro tipo I; Poder; Monte Carlo; Não balanceamento.

Ano: 2010

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1413-70542010000400008

Silva,Roberta Bessa Veloso; Ferreira,Daniel Furtado; Nogueira,Denismar Alves.

The present work emphasizes the importance of testing hypothesis on homogeneity of covariance matrices from multivariate k populations. The violation of the assumption of the homogeneity of covariance matrices affects the performance of the tests and the coverage probability of the confidence regions. This work intends to apply two tests of homogeneity of covariance and to evaluate type I error rates and power using Monte Carlo simulation in normal populations and robustness in non normal populations. Multivariate Bartlett's test (MBT) and its bootstrap version (MBTB) were used. Different configurations are tested combining sample sizes, number of variates, correlation and number of populations. Results show that the bootstrap test was considered superior...

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

Palavras-chave: Simulation type I error rate power; Monte Carlo.

Ano: 2008

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1413-70542008000100023

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...