Resumo

BOCA, R.T et al. Estimación del volumen sin corteza en Eucalyptus grandis utilizando modelos de regresión con variables instrumentales en dos etapas de plantaciones de la Mesopotamia argentina. RIA. Rev. investig. agropecu. [online]. 2015, vol.41, n.2, pp.201-207. ISSN 1669-2314.

For this work, total volume under bark (vtsc) and total volume over bark (vtcc) prediction models for individual trees were adjusted simultaneously. The total vtcc was adjusted based on the tree’s height (h) and diameter at breast height (dbh), and the total vtsc was simultaneously adjusted based on vtcc predictions. This simultaneous causality could create a bias in coefficients using traditional estimation methods with ordinary least squares (OLS), which could be removed resorting to two-stage least squares (2SLS) regression models. This work compares conventional methodologies used in the area and 2SLS methods. The data used comes from Eucalyptus grandis plantations set in four different agroclimatic zones in the Argentine Mesopotamia region Results show that it is possible to achieve adjustment models with low correlation in residuals and complying with the assumptions necessary to implement this methodology.

Palavras-chave : Prediction model; Instrumental variables; Argentinian Mesopotamia.

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