Setting confidence limits to genetic parameters estimated by restricted maximum likelihood analysis of North Carolina design II experiments

Abstract

The properties of the sampling distributions of additive and nonadditive genetic variances and narrow-sense heritabilities were investigated by means of a computer simulation study. Commonly used formulae for the standard errors of these quantities have been tested by means of the coverage probabilities of confidence intervals set using them. Approximate confidence intervals were set assuming a Normal distribution. Formulae that are based on the 'delta' technique, and are shown to produce reliable estimates of the standard errors of additive and nonadditive genetic variances and narrow-sense heritabilities, are provided. Confidence intervals for estimates of the narrow-sense heritability, based on the F- distribution, were tested and found to be conservative. A worked example provides an empirical appraisal of the methods of setting confidence limits to genetic parameters estimated by restricted maximum likelihood analysis of North Carolina design II experiments. Suitable statistical software is suggested for obtaining the standard errors of the genetic parameters by the 'delta' technique.