Published correlational effect sizes in social and developmental psychology

The distribution of effect sizes may offer insights about the research
done and reported in a scientific field. We have evaluated 12,412 manually
collected correlation effect sizes (Sample 1) and 31,157
computer-extracted correlation effect sizes (Sample 2) published in
journals focused on social or developmental psychology. Sample 1 consisted
of 243 studies from 6 journals published in 2010 and 2019. Sample 2
consisted of 5,012 papers published in 10 journals between 2010–2019. The
25th, 50th and 75th effect size percentiles were 0.08, 0.17 and 0.33, and
0.17, 0.31, and 0.52 in Samples 1 and 2, respectively. Sample 2
percentiles were probably larger because Sample 2 only included effect
sizes from the text but not from tables. In text, authors may have
emphasized larger correlations. Large sample sizes were associated with
smaller reported correlations. In Sample 1 about 70% of studies specified
a directional hypothesis. In 2010, no papers had power calculations while
in 2019, 14% of papers had power calculations. These data offer empirical
insights into the distribution of reported correlations and may inform the
interpretation of effect sizes. They also demonstrate the importance of
computation of statistical power and highlight potential reporting bias.