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Control Groups

  1. Stephanie Green

Published Online: 10 JAN 2014

DOI: 10.1002/0471667196.ess7277

Encyclopedia of Statistical Sciences

Encyclopedia of Statistical Sciences

How to Cite

Green, S. 2014. Control Groups. Encyclopedia of Statistical Sciences. 1–9.

Author Information

  1. Pfizer, Inc., Clinical Biostatistics, New London, Connecticut

Publication History

  1. Published Online: 10 JAN 2014


Use of appropriate control groups is a critical principle in clinical research methods. The modern randomized controlled trial is the most convincing and reliable method for minimizing bias and demonstrating effectiveness of treatment. Control groups for randomized trials may be patients randomized to no treatment, a placebo, or standard active therapy with or without a placebo. Due to practical and ethical constraints not all clinical questions can be addressed with a well-controlled randomized trial. Non-randomized trials can have specific comparator groups or be controlled in the sense that carefully chosen historical information from the literature is used for reference.


  • Control group;
  • placebo control;
  • historical control;
  • active control;
  • randomized controlled trial