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ERIC Number: EJ1090515
Record Type: Journal
Publication Date: 2016-Mar
Pages: 30
Abstractor: As Provided
ISSN: ISSN-0034-6543
Estimating the Difference between Published and Unpublished Effect Sizes: A Meta-Review
Polanin, Joshua R.; Tanner-Smith, Emily E.; Hennessy, Emily A.
Review of Educational Research, v86 n1 p207-236 Mar 2016
Practitioners and policymakers rely on meta-analyses to inform decision making around the allocation of resources to individuals and organizations. It is therefore paramount to consider the validity of these results. A well-documented threat to the validity of research synthesis results is the presence of publication bias, a phenomenon where studies with large and/or statistically significant effects, relative to studies with small or null effects, are more likely to be published. We investigated this phenomenon empirically by reviewing meta-analyses published in top-tier journals between 1986 and 2013 that quantified the difference between effect sizes from published and unpublished research. We reviewed 383 meta-analyses of which 81 had sufficient information to calculate an effect size. Results indicated that published studies yielded larger effect sizes than those from unpublished studies ( d[superscript bar over d] = 0.18, 95% confidence interval [0.10, 0.25]). Moderator analyses revealed that the difference was larger in meta-analyses that included a wide range of unpublished literature. We conclude that intervention researchers require continued support to publish null findings and that meta-analyses should include unpublished studies to mitigate the potential bias from publication status.
SAGE Publications. 2455 Teller Road, Thousand Oaks, CA 91320. Tel: 800-818-7243; Tel: 805-499-9774; Fax: 800-583-2665; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: Institute of Education Sciences (ED)
Authoring Institution: N/A
IES Funded: Yes
Grant or Contract Numbers: R305B100016