Comments on “Predicting the Mature Stature of Preadolescent Children” by Darrell Bock

Abstract

Bock presents an approach to adult height prediction based on fitting the triple-logistic growth function (Bock & Thissen, 1980) to individual height data. It is of importance, both to understanding the implications of Bock’s approach and to the following comments, that the significance of the Maximum A Posteriori (MAP) estimation of function parameters is realised. The present use of growth functions or models is made possible only in the presence of suitable data. These data must have more individual data points than the number of parameters in the function to be fitted. For a Preece-Baines Model 1 fit for example (Preece & Baines, 1978) at least 6 data points must be present to fit the 5 parameter model. Similarly for the 9 parameter triple-logistic (Bock & Thissen, 1980) at least 10 data points must be present. The satisfaction of these criteria poses obvious problems to research workers wanting to predict adult stature, interpolate or extrapolate data or derive biological parameters, such as peak height velocity, from functions fitted to few data points.