Effect size

Health Management Glossary

Research Methods

Definition. An effect size is a quantitative measure of the magnitude of a relationship or difference, independent of sample size.

Explanation

Funder and Ozer argue that small effects can be important when accumulated and that conventional benchmarks are misleading (Funder & Ozer, 2019). Effect sizes are essential for power analysis and sample size planning (Giner-Sorolla et al., 2024).

Related concepts

Sample size and statistical power Meta-analysis Moderation analysis

Read on The Health Topics

• The Sense and Nonsense of Effect Size: What Does Funder and Ozer’s (2019) Call Mean for Health Research?
• Understanding Statistical Power Analysis in Psychology

References

Funder, D. C., & Ozer, D. J. (2019). Evaluating effect size in psychological research: Sense and nonsense. Advances in Methods and Practices in Psychological Science, 2(2), 156–168. doi:10.1177/2515245919847202 (with the 2020 corrigendum).

Giner-Sorolla, R., Montoya, A. K., Reifman, A., Carpenter, T., Lewis Jr, N. A., Aberson, C. L., … & Soderberg, C. (2024). Power to detect what? Considerations for planning and evaluating sample size. Personality and Social Psychology Review, 28 (3), 276-301.

Cite this entry: Kurutkan, M. N. (2026). Effect size. In The Health Topics glossary. https://healthtopic.org/glossary/effect-size/

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