GTRACK - A PC PROGRAM FOR COMPUTING GOLDSTEINS GROWTH CONSTANCY INDEXAND AN ALTERNATIVE MEASURE OF TRACKING

This paper reviews Goldstein's 'growth constancy index,' xi, a measure of tracking which can be used to determine whether or not individuals maintain their relative positions in the distribution of a given meas urement as that distribution changes over time. We suggest that xi is an appropriate measure of tracking when the (standardized) measurement s arise in the context of a Model I ANOVA, but that the intraclass cor relation coefficient, r(l), may be preferred when a Model II ANOVA is applicable. We also describe - and make available - a PC program which allows the user to choose between Model I and Model II, and computes the appropriate tracking index and confidence intervals for the corres ponding parameter.