Abstract
When plant type indices are given by the quotients of two quantitative traits following normal law, the statistical means are studied to evaluate, from statistics of component traits, (1) heritability value of the indices, (2) the regression function of the quotient on its component traits and (3) the correlation coefficient between components and the quotient. And the usefulness of such indices are suggested as the result of the application of these means to the experimental data in rice breeding.
