Comparisons and Conversions: A Methodological Note and Caution for Meta-Analysis in Sport and Exercise Psychology.

Meta-analysis is a powerful tool in sport and exercise psychology. However, it has a number of pitfalls, and some lead to ill-advised comparisons and overestimation of effects. The impetus for this research note is provided by a recent systematic review of meta-analyses that examined the correlates of sport performance and has fallen foul of some of the pitfalls. Although the systematic review potentially has great value for researchers and practitioners alike, it treats effects from correlational and intervention studies as yielding equivalent information, double-counts multiple studies, and uses an effect size for correlational studies (Cohen's d) that provides an extreme contrast of unclear practical relevance. These issues impact interpretability, bias, and usefulness of the findings. This methodological note explains each pitfall and illustrates use of an appropriate equivalent effect size for correlational studies (Mathur and VanderWeele's d) to help researchers avoid similar issues in future work.