Sample size and the estimation of physiological parameters in the field

Abstract

Summary Estimates of basal rate of metabolism in fruit pigeons and flying foxes, derived from the mean of individual means, were compared to the mean basal rate obtained by pooling all data into a single estimate. Pooled estimates of basal rate differ by ≤1% of the basal rates obtained from the mean of individual means in 7 of 10 species of pigeons and 4 of 11 species of flying foxes. The coefficient of variation of the mean of individual mean basal rates decreased with an increase in the mean number of measurements per individual, which, given that the number of measurements per individual was 8·4 in pigeons and 3·8 in flying foxes, partially accounts for the smaller coefficients in pigeons. The maximal absolute difference between individual mean basal rates and the mean of individual means within a species decreased with an increase in the number of measurements per individual to 8, beyond which the difference remained constant. Repeated measurements on a single individual usually gave an estimate of basal rate within 2–8% of the species’ mean when eight or more measurements were made. . The analysis of limited samples most often occurs in the study of elusive or endangered species, when the availability of individuals for study is greatly limited.