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On the Variability of Harvest Indices
Author(s) -
Hühn M.
Publication year - 1990
Publication title -
journal of agronomy and crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.095
H-Index - 74
eISSN - 1439-037X
pISSN - 0931-2250
DOI - 10.1111/j.1439-037x.1990.tb00817.x
Subject(s) - yield (engineering) , mathematics , grain yield , variance (accounting) , rapeseed , index (typography) , coefficient of variation , statistics , agronomy , physics , thermodynamics , biology , computer science , accounting , world wide web , business
The harvest index Z is defined, for example for cereals, as the ratio between grain yield X and biological yield Y: Z = X/Y. For many purposes the variance of Z is of major interest. In this paper several approximations for this variance are derived and their accuracy was investigated. These explicit formulae depend on some characteristics (means, variances or coefficients of variation, covariances or correlations) of the component variables grain yield X and biological yield Y. It is shown that for most practical applications the approximation v 2 z = v 2 x + v 2 y ‐ 2rv x v y provides a sufficient accuracy for numerical calculations (v x v y and v z are the coefficients of variation for grain yield X, biological yield Y and harvest index Z and r denotes the correlation coefficient between X and Y). Some conclusions on the relations between v x , v y and v z are derived. Finally, all the theoretical investigations and results are demonstrated and applied to a numerical example of winter‐rapeseed data.