COMPUTATION OF FOULKES AND DAVIS NONPARAMETRIC TRACKING INDEX USING GAUSS

Foulkes and Davis (1981) define tracking as the maintenance of relative rank over a given time span. This paper outlines the development of their statistic, based on a set of individual growth profiles, which estimates the degree of tracking observed in a one-sample longitudinal data set and shows how confidence intervals for the corresponding population parameter may be constructed. An example using a measure of skeletal growth is given and a GAUSS program to do the computations is provided. (Information on obtaining the GAUSS program is provided in the Appendix.) Properties of this statistical approach to tracking are contrasted with another non-parametric method based on Cohen's kappa statistic.