Issues in the design and interpretation of studies to evaluate the impact of community-based interventions

Trop Med Int Health. 1997 Nov;2(11):1022-9. doi: 10.1046/j.1365-3156.1997.d01-188.x.


Increasingly, epidemiologists are faced with the need to evaluate the impact of an intervention that is delivered at the level of a community or cluster of individuals, rather than at the individual level. This has profound implications for the design and interpretation of a study to evaluate its impact. We start by discussing the issues arising in the extension of the randomized double-blind controlled trial methodology to the evaluation of interventions delivered to clusters of individuals, or to whole communities, where the unit of randomization is a cluster of individuals rather than an individual. We then consider alternative approaches to design, discuss their relative strengths and weaknesses and present a framework of design options. Finally we propose a pragmatic approach to evaluation design in this setting. We believe that the answer lies in the judicious selection of different design elements, combined in such a way that when the evidence from each is presented together, a clear picture of the impact of the intervention emerges. We illustrate this using an example from the recent literature.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Community Medicine
  • Epidemiologic Research Design*
  • Evaluation Studies as Topic
  • Humans
  • Randomized Controlled Trials as Topic / methods*