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  1. Timothy M. M. Farley

Published Online: 15 JUL 2005

DOI: 10.1002/0470011815.b2a08045

Encyclopedia of Biostatistics

Encyclopedia of Biostatistics

How to Cite

Farley, T. M. M. 2005. Reproduction. Encyclopedia of Biostatistics. 7.

Author Information

  1. World Health Organisation, Geneva, Switzerland

Publication History

  1. Published Online: 15 JUL 2005


Assessing objectively the efficacy and effectiveness of contraceptive methods is challenging because of the large number of different factors affecting the intrinsic fertility of a couple, the timing of intercourse, and the way the method is used. While effectiveness, or the typical use pregnancy rate, is easier to observe, it is difficult to generalize to other populations since it includes behavioral factors, such as how or whether the method was used. By contrast, efficacy, or the perfect use pregnancy rate, can be indirectly estimated from patterns of intercourse and method use, and is more easily generalized to other women or couples. For methods that are not coitus-dependent, typical and perfect use pregnancy rates are similar, but can be very different for methods requiring a high degree of user compliance.


  • contraception;
  • efficacy;
  • effectiveness;
  • fertility;
  • estimation;
  • generalizability