A meta-analysis of coefficient alpha for the Impact of Event Scales: A reliability generalization study

Matt Vassar, Kayce G. Knaup, William Hale, Heather Hale

Research output: Contribution to journalArticle

2 Scopus citations


We conducted a score reliability meta-analysis across studies using the Impact of Event Scales. Five hundred and ninety-four studies using the measure were located through electronic database searches and then separated to identify studies that had calculated and reported reliability coefficients from their own data. The 66 articles that remained were then coded to identify potential study characteristics that might influence the variation in reliability estimates. Results indicate adequate internal consistency estimates for all subscales across both scale versions. Furthermore, coefficient alpha was positively correlated with studies involving war and abuse victims for the IES Avoidance subscale. The alpha coefficient was also positively correlated with the percentage of female participants for the Intrusion subscale and negatively correlated to journal type for the composite reliability estimate. Results from this study provide useful information, in terms of scale performance, for researchers interested in using the scale for future academic pursuits and for school psychologists. In particular, implications for school psychologists are considered.

Original languageEnglish
Pages (from-to)6-16
Number of pages11
JournalSouth African Journal of Psychology
Issue number1
StatePublished - Mar 2011



  • IES
  • Impact of event scale
  • Meta-analysis
  • PTSD
  • Reliability
  • Reliability generalization

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