Confidence Intervals for Ages of Marsupials Determined from Body Measurements

Abstract

Fitted growth curves for several individual animals for a measurement such as head length will often differ significantly from each other, even though the curves all have the same general form. For construction of a confidence interval for the age of an animal of unknown age with a particular head length, account should be taken of between-animal variation as well as within-animal variation. This paper gives methods for estimating the components of the variation from observations on animals of known age, and for combining them to give approximate confidence intervals for the age of animals of unknown age. The methods are illustrated using data from grey kangaroos.