PC program for assessing the relationship between rate of change and initial value.
Additional Document Info
A menu-driven PC program implementing Blomqvist's [J. Am. Stat. Assn. 72, 746-749, 1977] method for assessing the relationship between rate of change and initial value is described, illustrated and made available. It is shown that the naive approach to this problem--computing the correlation between the initial value and either the amount or rate of change--results in a negatively biased estimator. The extent of this bias can be dramatic and may lead investigators to conclude that a negative correlation is present when none exists; or that there is no correlation when in fact the correlation is positive. Blomqvist's (maximum likelihood) estimator avoids this bias, and is obtained by a transformation of the naive estimator.