This article by Joseph A. Durlak from Loyola University Chicago provides guidelines for selecting, calculating, and interpreting effect sizes (ESs) in research. It emphasizes the importance of ESs in understanding the magnitude and direction of differences between groups or relationships between variables. The article discusses different types of ESs commonly used in group and correlational studies, including raw mean differences, standardized mean differences (SMDs), odds ratios (ORs), and product-moment correlations (r). It highlights the need to report ESs alongside p-values and confidence intervals (CIs) to provide a comprehensive understanding of research findings. The article also addresses the challenges of small sample sizes in pediatric studies and the importance of considering the practical or clinical significance of ESs. It offers practical advice on calculating and interpreting ESs, including the use of various equations and resources for different research designs. The article concludes by emphasizing the role of ESs in enhancing the quality and interpretability of research reports.This article by Joseph A. Durlak from Loyola University Chicago provides guidelines for selecting, calculating, and interpreting effect sizes (ESs) in research. It emphasizes the importance of ESs in understanding the magnitude and direction of differences between groups or relationships between variables. The article discusses different types of ESs commonly used in group and correlational studies, including raw mean differences, standardized mean differences (SMDs), odds ratios (ORs), and product-moment correlations (r). It highlights the need to report ESs alongside p-values and confidence intervals (CIs) to provide a comprehensive understanding of research findings. The article also addresses the challenges of small sample sizes in pediatric studies and the importance of considering the practical or clinical significance of ESs. It offers practical advice on calculating and interpreting ESs, including the use of various equations and resources for different research designs. The article concludes by emphasizing the role of ESs in enhancing the quality and interpretability of research reports.