A computer pattern recognition system, RAPID, has been used to study the spontaneous motor activity of Sprague-Dawley rats. This system produces a large number of measures of the activity of control and experimental groups in any given study. The large number of measures involved presents a problem when one attempts to decide whether the behavioral activity of the exposed group differs from that of the control group. Extensive Monte Carlo studies have been performed in an attempt to develop and validate a simple statistic to be used in such decisions.