The University of Southampton
University of Southampton Institutional Repository

Some general points on the I^2 measure of heterogeneity in meta-analysis

Some general points on the I^2 measure of heterogeneity in meta-analysis
Some general points on the I^2 measure of heterogeneity in meta-analysis
Meta-analysis has developed to be a most important tool in evaluation research. Heterogeneity is an issue that is present in almost any meta-analysis. However, the magnitude of heterogeneity differs across meta-analyses. In this respect, Higgins’ I2 has emerged to be one of the most used and, potentially, one of the most useful measures as it provides quantification of the amount of heterogeneity involved in a given meta-analysis. Higgins’ I2 is conventionally interpreted, in the sense of a variance component analysis, as the proportion of total variance due to heterogeneity. However, this interpretation is not entirely justified as the second part involved in defining the total variation, usually denoted as s2, is not an average of the study-specific variances, but in fact some other function of the study-specific variances. We show that s2 is asymptotically identical to the harmonic mean of the study-specific variances and, for any number of studies, is at least as large as the harmonic mean with the inequality being sharp if all study-specific variances agree. This justifies, from our point of view, the interpretation of explained variance, at least for meta-analyses with larger number of component studies or small variation in study-specific variances. These points are illustrated by a number of empirical meta-analyses as well as simulation work.
685-695
Bohning, Dankmar
1df635d4-e3dc-44d0-b61d-5fd11f6434e1
Holling, Heinz
88d46f56-77ca-4d0e-b035-a51aff735435
Lerdsuwnasri, Rattana
c2e5269d-3836-49d0-8989-753e6e33dc35
Bohning, Dankmar
1df635d4-e3dc-44d0-b61d-5fd11f6434e1
Holling, Heinz
88d46f56-77ca-4d0e-b035-a51aff735435
Lerdsuwnasri, Rattana
c2e5269d-3836-49d0-8989-753e6e33dc35

Bohning, Dankmar, Holling, Heinz and Lerdsuwnasri, Rattana (2017) Some general points on the I^2 measure of heterogeneity in meta-analysis. Metrika, 80 (6-8), 685-695. (doi:10.1007/s00184-017-0622-3).

Record type: Article

Abstract

Meta-analysis has developed to be a most important tool in evaluation research. Heterogeneity is an issue that is present in almost any meta-analysis. However, the magnitude of heterogeneity differs across meta-analyses. In this respect, Higgins’ I2 has emerged to be one of the most used and, potentially, one of the most useful measures as it provides quantification of the amount of heterogeneity involved in a given meta-analysis. Higgins’ I2 is conventionally interpreted, in the sense of a variance component analysis, as the proportion of total variance due to heterogeneity. However, this interpretation is not entirely justified as the second part involved in defining the total variation, usually denoted as s2, is not an average of the study-specific variances, but in fact some other function of the study-specific variances. We show that s2 is asymptotically identical to the harmonic mean of the study-specific variances and, for any number of studies, is at least as large as the harmonic mean with the inequality being sharp if all study-specific variances agree. This justifies, from our point of view, the interpretation of explained variance, at least for meta-analyses with larger number of component studies or small variation in study-specific variances. These points are illustrated by a number of empirical meta-analyses as well as simulation work.

Text
Metrika_Higgins_R2 - Accepted Manuscript
Download (272kB)
Text
some general points - Version of Record
Available under License Creative Commons Attribution.
Download (488kB)

More information

Accepted/In Press date: 22 July 2017
e-pub ahead of print date: 22 July 2017

Identifiers

Local EPrints ID: 419454
URI: http://eprints.soton.ac.uk/id/eprint/419454
PURE UUID: 0c60439c-c2f9-4ba2-a103-3ce369f05ab0
ORCID for Dankmar Bohning: ORCID iD orcid.org/0000-0003-0638-7106

Catalogue record

Date deposited: 12 Apr 2018 16:30
Last modified: 17 Dec 2019 01:39

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×