Heterogeneity: the issue of apples, oranges and fruit pie

Epidemiol Psychiatr Sci. 2012 Mar;21(1):27-9. doi: 10.1017/s2045796011000643.


Heterogeneity refers to any kind of variation among studies contributing to the same outcome in a systematic review. There are three broad types of heterogeneity: clinical heterogeneity, methodological heterogeneity and statistical heterogeneity. In this paper, we describe these three types of heterogeneity and the main statistical approaches to measure heterogeneity.

MeSH terms

  • Computer Graphics
  • Confidence Intervals
  • Data Interpretation, Statistical*
  • Humans
  • Meta-Analysis as Topic
  • Research / statistics & numerical data*
  • Review Literature as Topic