This article demonstrates that sole reliance on tests of statistical significance in the analysis and interpretation of neuropsychological data that is grounded in quasi-experimentation can systematically confound the conclusions drawn from our neuropsychological research regarding brain-behavior relations. The conclusion of this article is that we must accompany the statistical significance test with more appropriate statistics--namely, point-estimate effect sizes along with interval estimation and meta-analysis for the analysis of data from multiple studies. The argument for this conclusion is demonstrated from the re-analysis of published neuropsychological test findings. It is recommended on the basis of this review that the consumer of neuropsychological reports will be better served if due consideration is given to the magnitude of effect in brain-behavior statistical analyses.