Interpreting Significance: The Differences Between Statistical Significance, Effect Size, and Practical Importance

It is a common misconception that statistical significance indicates a large and/or important effect. In fact the three concepts—statistical significance, effect size, and practical importance—are distinct from one another and a favorable result on one dimension does not guarantee the same on any other. In this article, we explain these concepts and distinguish between them. Finally, we propose reporting confidence intervals as a step toward disambiguating these concepts.

Keywords: Confidence intervals, Effect size, Clinical significance, Misconceptions