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J Hum Reprod Sci. 2012 Jan;5(1):7-13. doi: 10.4103/0974-1208.97779.

Sample size estimation and power analysis for clinical research studies.

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Department of Biostatistics, National Institute of Animal Nutrition and Physiology, Bangalore, India.


Determining the optimal sample size for a study assures an adequate power to detect statistical significance. Hence, it is a critical step in the design of a planned research protocol. Using too many participants in a study is expensive and exposes more number of subjects to procedure. Similarly, if study is underpowered, it will be statistically inconclusive and may make the whole protocol a failure. This paper covers the essentials in calculating power and sample size for a variety of applied study designs. Sample size computation for single group mean, survey type of studies, 2 group studies based on means and proportions or rates, correlation studies and for case-control for assessing the categorical outcome are presented in detail.


Correlation; odds ratio; power; prevalence; proportions; sample size; survey

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