+**Effect Size** measures the strength of a phenomenon or the magnitude of a relationship observed in a study. It moves beyond "if" a difference exists, offering a direct, interpretable measure of its practical importance, distinct from [P-value](/wiki/P-value) and complementing [Statistical Significance](/wiki/Statistical_Significance).
+## See also
+- [Statistical Power](/wiki/Statistical_Power)
+- [Confidence Interval](/wiki/Confidence_Interval)
+- [Meta-analysis](/wiki/Meta-analysis)