Health, Fitness & Dieting, Forensic Medicine 

Well designed studies are vital to provide information for the efficient planning, operation, monitoring and evaluation of health services. For any such study - whether of the efficacy of an immunization programme or of the availability of maternity care- the decision on how large a sample to select from the population in question must take into account the need both to obtain statistically valid results and to avoid unnecessary expenditure of time and resources.

This manual has been prepared to provide guidance for health workers and managers responsible for making such decisions, and in particular for those undertaking studies at local or district level without detailed knowledge of statistical methodology. It presents a variety of situations in which minimum sample size must be determined, including studies to estimate population proportion, odds ratio, relative risk and disease incidence. The illustrative examples of health studies are accompanied by over fifty tables that enable the reader to determine the sample size required without resource to complicated calculations.

The manual is not intended to help the reader decide what type of study, confidence level or degree of precision is most appropriate, nor does it discuss the theoretical basis of sample size determination. It is designed to be used in "cookbook" fashion as a practical guide to making decisions on sample size once a proposed study and its objectives have been clearly defined.