The Journal of general psychology
-
Review
Are effect sizes and confidence levels problems for or solutions to the null hypothesis test?
Some have proposed that the null hypothesis significance test, as usually conducted using the t test of the difference between means, is an impediment to progress in psychology. To improve its prospects, using Neyman-Pearson confidence intervals and Cohen's standardized effect sizes, d, is recommended. ⋯ This essay was written to remind us that the t test, based on the sample--not the true--standard deviation, does not apply solely to distance between means. The t test pertains to a much more ambiguous specification: the difference between samples, including sampling variations of the standard deviation.