Abstract
Over-reliance on significance testing has been heavily criticized in psychology. Therefore the American Psychological Association recommended supplementing the p value with additional elements such as effect sizes, confidence intervals, and considering statistical power seriously. This article elaborates the conclusions that can be drawn when these measures accompany the p value. An analysis of over 30 summary papers (including over 6,000 articles) reveals that, if at all, only effect sizes are reported in addition to p’s (38%). Only every 10th article provides a confidence interval and statistical power is reported in only 3% of articles. An increase in reporting frequency of the supplements to p’s over time owing to stricter guidelines was found for effect sizes only. Given these practices, research faces a serious problem in the context of dichotomous statistical decision making: since significant results have a higher probability of being published (publication bias), effect sizes reported in articles may be seriously overestimated.
Get full access to this article
View all access options for this article.
