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	効果量	What Works Clearinghouse Standards
分野	研究統計	Education
系統	Process / pipeline	Process / pipeline
提唱年	1988	2022
提唱者	Jacob Cohen	Institute of Education Sciences (IES), U.S. Department of Education
種類	Concept	Standards and procedures for assessing the causal credibility of education studies
原典	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.
別名	ES, Cohen's d, standardized effect, practical significance	WWC Standards, WWC Evidence Standards, What Works Clearinghouse Review, WWC Study Rating
関連	4	3
概要	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.