Reproducible research in sport and exercise psychology: The role of sample sizes.

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Abstract

Objectives: We aim to introduce the discussion on the crisis of confidence to sport and exercise psychology. We focus on an important aspect of this debate, the impact of sample sizes, by assessing sample sizes within sport and exercise psychology. Researchers have argued that publications in psychological research contain numerous false-positive findings and inflated effect sizes due to small sample sizes. Method: We analyse the four leading journals in sport and exercise psychology regarding sample sizes of all quantitative studies published in these journals between 2009 and 2013. Subsequently, we conduct power analyses. Results: A substantial proportion of published studies does not have sufficient power to detect effect sizes typical for psychological research. Sample sizes and power vary between research designs. Although many correlational studies have adequate sample sizes, experimental studies are often underpowered to detect small-to-medium effects. Conclusions: As sample sizes are small, research in sport and exercise psychology may suffer from false-positive results and inflated effect sizes, while at the same time failing to detect meaningful small effects. Larger sample sizes are warranted, particularly in experimental studies.