Maternal smoking during pregnancy and birthweight - A propensity score matching approach

There is accumulated evidence of the existence of a deleterious effect of smoking on birth outcomes. Understanding the effect of smoking on pregnancy is a critical issue because of the public policy implications for dissuading maternal smoking. We explore this issue by using the propensity score method and compare that with parametric estimators. First we estimate the treatment effect of smoking during pregnancy on different birth outcomes. Then, we extend the method to the case of the multi-treatment "intensity of smoking". The deleterious effect of smoking is found robust to the different estimation methods used.Smoking, birth outcomes, causal effects, propensity score and matching

Maternal smoking during pregnancy and birthweight : a propensity score matching approach

There is accumulated evidence of the existence of a deleterious effect of smoking on birth outcomes. Whether there is a causal link or a mere statistical association is not clear. Understanding the effect of smoking on pregnancy is a critical issue because of the public policy implications for dissuading maternal smoking. This study was designed to distinguish causal links from statistical association in the relationship between fetal exposure to maternal smoking and birth outcomes. Although the task involves several aspects of estimation we restrict our focus to the issue of self-selection. We explore this issue by using the propensity score method and compare that with parametric estimators. First we estimate the treatment effect of smoking during pregnancy on different birth outcomes. Then, we extend the method to the case of the multi-treatment “intensity of smoking”. The deleterious effect of smoking is found robust to the different estimation methods used.Fundação para a Ciência e a Tecnologia (FCT

Produção forrageira e valor nutritivo do capim elefante (Pennisetum purpureum Schum.) vars. Anã e Cameron.

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Sistemas silvipastoris na Amazônia Oriental.

A problemática das pastagens. Os sistemas silvipastoris (SSP). O papel da árvore. Interação árvore - pastagem. Componente animal. Sistemas silvipastoris praticados na Amazônia Oriental. Avaliação de sistemas silvipastoris. Adoção de sistemas silvipastoris.bitstream/item/63268/1/Oriental-Doc56.pd

Características do solo e de pastagens em sistemas de produção leiteira em Uruará, Pará.

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Manejo das pastagens de quicuio-da-amazônia e andropogon em Paragominas, PA.

bitstream/item/57424/1/CPATU-ComTec59.pd

Bayesian estimation of inefficiency heterogeneity in stochastic frontier models

Estimation of the one sided error component in stochastic frontier models may erroneously attribute firm characteristics to inefficiency if heterogeneity is unaccounted for. However, unobserved inefficiency heterogeneity has been little explored. In this work, we propose to capture it through a random parameter which may affect the location, scale, or both parameters of a truncated normal inefficiency distribution using a Bayesian approach. Our findings using two real data sets, suggest that the inclusion of a random parameter in the inefficiency distribution is able to capture latent heterogeneity and can be used to validate the suitability of observed covariates to distinguish heterogeneity from inefficiency. Relevant effects are also found on separating and shrinking individual posterior efficiency distributions when heterogeneity affects the location and scale parameters of the one-sided error distribution, and consequently affecting the estimated mean efficiency scores and rankings. In particular, including heterogeneity simultaneously in both parameters of the inefficiency distribution in models that satisfy the scaling property leads to a decrease in the uncertainty around the mean scores and less overlapping of the posterior efficiency distributions, which provides both more reliable efficiency scores and rankings