Abstract

For years, researchers have been applying a variety of statistics to obtain outcome measures for free-response extrasensory perception studies without knowing which measure is the most sensitive. Recently the choice has tended to be between direct hits and sums of ranks, with direct hits the most popular. However, according to different theoretical models of psi functioning and of judging practices, either measure could be superior. If researchers are using the wrong measure then statistical power is lost and more (time-consuming) trials than necessary must be conducted in a study to obtain either statistical significance or an accurate estimate of effect size. To determine whether direct hits or ranks are the more sensitive measure, J. Milton sought both outcome measures for all free-response ESP studies published in the last 5 yrs. Data were obtained for 46 studies, including 42 ganzfeld studies. Overall, the cumulation of the studies\' outcomes was statistically signi!ficantly above chance. On average, sums of ranks outperformed direct hits in terms of both effect sizes and p values, but not to a statistically significant degree.