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	Effect Size in Education Research	効果量
分野	Education	研究統計
系統	Process / pipeline	Process / pipeline
提唱年	1988	1988
提唱者	Statistical methodology (Cohen; Glass; Hedges & Olkin) applied in education	Jacob Cohen
種類	Standardized index of the magnitude of an effect or difference	Concept
原典	Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences (2nd ed.). Lawrence Erlbaum Associates. ISBN: 9780805802832	Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences (2nd ed.). Lawrence Erlbaum Associates. ISBN: 0-8058-0283-5
別名	Educational Effect Size, Standardized Mean Difference in Education, Hedges' g in Education, Effect Size Reporting	ES, Cohen's d, standardized effect, practical significance
関連	2	4
概要	An effect size is a standardized, scale-free measure of the magnitude of a difference or relationship — how big an effect is, not just whether it is statistically significant. In education research it is the common currency for reporting intervention impacts and for combining studies in meta-analysis, with the standardized mean difference (Cohen's d, or its bias-corrected form Hedges' g) the most familiar. Effect sizes let researchers compare effects across studies, outcomes, and scales, and translate statistical results into terms practitioners can weigh.	Effect size quantifies the magnitude of a research finding independent of sample size. While a p-value tells you whether a result is statistically significant, an effect size tells you how big the result is. Jacob Cohen formalized effect size measurement in behavioral sciences (1988), establishing standard benchmarks (small = 0.2, medium = 0.5, large = 0.8 for Cohen's d). Effect sizes are essential for meta-analysis, power analysis, and communicating the practical importance of research findings.