Title

Assessing heterogeneity in meta-analysis: Q statistic or I2 index?

Document Type

Article

Abstract

In meta-analysis, the usual way of assessing whether a set of single studies is homogeneous is by means of the Q test. However, the Q test only informs meta-analysts about the presence versus the absence of heterogeneity, but it does not report on the extent of such heterogeneity. Recently, the IČ index has been proposed to quantify the degree of heterogeneity in a meta-analysis. In this article, the performances of the Q test and the confidence interval around the IČ index are compared by means of a Monte Carlo simulation. The results show the utility of the IČ index as a complement to the Q test, although it has the same problems of power with a small number of studies.

Comments

Reprinted from Psychological Assessment, Vol.11, Issue 2, June 2006, pp. 193-206 'This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.' Homepage for journal Psychological Assessment: http://www.apa.org/journals/pas/