Report tau or exp(tau) rather than tau-squared in random-effects meta-analyses

Chatfield, Mark D., Marquart-Wilson, Louise, Dobson, Annette and Farewell, Daniel ORCID: https://orcid.org/0000-0002-8871-1653 2026. Report tau or exp(tau) rather than tau-squared in random-effects meta-analyses. Research Synthesis Methods 10.1017/rsm.2026.10075

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Abstract

In random-effects meta-analysis, the between-study heterogeneity variance, , is often reported but is not easy to interpret. For meta-analyses of differences (such as mean differences, standardized mean differences, or risk differences), the standard deviation (SD), , indicates the extent to which studies’ true effects vary about their average. For meta-analyses of (natural) log-transformed measures of effect (such as log risk ratios [RRs]), we explain how the geometric SD, , is helpful to understand how untransformed measures (such as RRs) vary multiplicatively about their average. We recommend that authors and software developers report for differences and for ratios, rather than . This will facilitate the interpretation of the magnitude of heterogeneity values, for example, the interpretation of heterogeneity estimates and confidence intervals beyond simple binary statements about the presence or absence of heterogeneity.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Medicine
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0, Type: open-access
Publisher:	Cambridge University Press
ISSN:	1759-2879
Date of First Compliant Deposit:	3 March 2026
Date of Acceptance:	9 January 2026
Last Modified:	03 Mar 2026 12:16
URI:	https://orca.cardiff.ac.uk/id/eprint/185415

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