A bootstrap approach to estimate reference intervals of biochemical variables in sheep using reduced sample sizes

This study presents a new statistical approach, based on data bootstrap, to estimate reference intervals for 12 blood biochemical variables in Sarda dairy sheep. The method was applied to real and simulated data from 120 to 40 animals. The reference intervals calculated with the new method remained quite constant as sample size decreased from 120 down to 60 animals, and became wider with fewer individuals. So, a minimum threshold of 60 animals could be considered a good limit to obtain reliable reference intervals for blood biochemical variables in Sarda dairy sheep. Moreover, comparisons between results from real and simulated data suggested that the method could be also applied to other laboratory variables.