Use of the estimated intraclass correlation for correcting differences in effect size by level

Soyeon Ahn, Nicolas D. Myers, Ying Jin

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


In a meta-analysis of intervention or group comparison studies, researchers often encounter the circumstance in which the standardized mean differences (d-effect sizes) are computed at multiple levels (e. g., individual vs. cluster). Cluster-level d-effect sizes may be inflated and, thus, may need to be corrected using the intraclass correlation (ICC) before being combined with individual-level d-effect sizes. The ICC value, however, is seldom reported in primary studies and, thus, may need to be computed from other sources. This article proposes a method for estimating the ICC value from the reported standard deviations within a particular meta-analysis (i. e., estimated ICC) when an appropriate default ICC value (Hedges, 2009b) is unavailable. A series of simulations provided evidence that the proposed method yields an accurate and precise estimated ICC value, which can then be used for correct estimation of a d-effect size. The effects of other pertinent factors (e. g., number of studies) were also examined, followed by discussion of related limitations and future research in this area.

Original languageEnglish (US)
Pages (from-to)490-502
Number of pages13
JournalBehavior Research Methods
Issue number2
StatePublished - Jun 2012


  • Intraclass correlation (ICC)
  • Level of analysis
  • Meta-analysis
  • Multilevel
  • Standardized mean difference

ASJC Scopus subject areas

  • Psychology(all)
  • Psychology (miscellaneous)
  • Experimental and Cognitive Psychology
  • Arts and Humanities (miscellaneous)
  • Developmental and Educational Psychology


Dive into the research topics of 'Use of the estimated intraclass correlation for correcting differences in effect size by level'. Together they form a unique fingerprint.

Cite this