A NOTE ON THE SKEWNESS OF THE FREQUENCY-DISTRIBUTION OF HARVEST INDEXES WITH AN APPLICATION TO WINTER OILSEED RAPE (BRASSICA-NAPUS L.)

Based on well-known statistical approximations for the mean. variance, and for the third moment about zero of the ratio of two random variab les, a general expression has been derived for the skewness of the dis tribution of harvest indices. The skewness of the distribution of harv est indices depends on three parameters: coefficients of variation for the two component traits and their correlation. Conclusions for the s ign of this skewness are discussed. Finally, the theoretical results a nd conclusions have been checked and applied to an experimental data s et of winter oilseed rape. The agreement between expected and observed skewness is extraordinary good.