A nonparametric comparison of monomolecular growth curves: application to western painted turtle data

Intractable distributional assumptions are generated in parametric analyses comparing groups of subjects described by nonlinear growth models. The distributional situation becomes more complex when pointwise mean curves best describe group growth (instead of curves based on mean parameters). An interval specific randomization test is developed to handle monomolecular growth models. The need for the technique was motivated by a study describing longitudinal growth data from the annuli on abdominal scutes of groups of western painted turtles. The analyses indicate that female turtles grow larger than male through the first seven years of life. The analytical procedures developed for these turtles are useful in the description and analyses of many other growth processes.