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	Effect Size in Education Research	Effektstorlek	What Works Clearinghouse Standards
Ämnesområde	Education	Forskningsstatistik	Education
Familj	Process / pipeline	Process / pipeline	Process / pipeline
Ursprungsår	1988	1988	2022
Upphovsperson	Statistical methodology (Cohen; Glass; Hedges & Olkin) applied in education	Jacob Cohen	Institute of Education Sciences (IES), U.S. Department of Education
Typ	Standardized index of the magnitude of an effect or difference	Concept	Standards and procedures for assessing the causal credibility of education studies
Ursprungskälla	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	What Works Clearinghouse. (2022). What Works Clearinghouse Procedures and Standards Handbook, Version 5.0. Institute of Education Sciences, U.S. Department of Education.
Alias	Educational Effect Size, Standardized Mean Difference in Education, Hedges' g in Education, Effect Size Reporting	ES, Cohen's d, standardized effect, practical significance	WWC Standards, WWC Evidence Standards, What Works Clearinghouse Review, WWC Study Rating
Närliggande	2	4	3
Sammanfattning	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.	The What Works Clearinghouse (WWC) standards are the protocol the U.S. Institute of Education Sciences uses to judge how much confidence an education study's findings deserve as causal evidence. They specify which designs can support causal claims, how to screen for threats such as attrition and confounding, and how to rate each study — Meets Standards Without Reservations, With Reservations, or Does Not Meet Standards — before synthesizing the body of evidence. The standards are a cornerstone of evidence-based education policy in the United States.