Sample Size Estimation in Clinical Trials




Sample size, Statistically significant, Clinically significant, Type I error, Type II error, Power


Sample size estimation remains as a cornerstone in the meticulous planning and execution of clinical trials, pivotal for ensuring studies possess the requisite statistical power to discern meaningful treatment effects. Insufficient sample sizes compromise the robustness of findings, whereas excessively large samples inflate costs and compromise data integrity. This article meticulously explains the multifaceted factors that outline sample size determination, encompassing various factors such as research design, types of hypotheses, error thresholds, effect size considerations, validity and precision. It investigates into the scope of methodologies available for sample size computation, spanning from intricate statistical formulas to pragmatic tabular approaches. Moreover, it underscores the significance of post-hoc power analysis in retrospectively evaluating completed studies, shedding light on their statistical robustness. This literature review furnishes a nuanced understanding of the sample size estimation landscape in clinical trials, delineating their strengths, limitations, and real-world applications. Anticipating participant attrition assumes paramount importance for proactively adjusting sample sizes, ensuring studies remain methodologically sound. Equipped with a profound grasp of these principles, researchers are empowered to conduct scientifically rigorous and impactful clinical trials, furnishing compelling evidence to inform judicious decision-making in healthcare interventions.


Zhong B. How to Calculate Sample Size in Randomized Controlled Trial? J Thorac Dis. 2009 Dec;1(1):51-4.

Zodpey SP. Sample size and power analysis in medical research. Indian J Dermatol Venereol Leprol. 2004;70(2):123-8.

Charles P, Giraudeau B, Dechartres A, Baron G, Ravaud P. Reporting of sample size calculation in randomised controlled trials: review. BMJ. 2009 May 12;338:b1732. Doi: PMid:19435763 PMCid:PMC2680945

Wang X, Ji X. Sample Size Estimation in Clinical Research. Chest. 2020 Jul;158(1):S12-20. Doi: PMid:32658647

Gupta KK, Attri JP, Singh A, Kaur H, Kaur G. Basic concepts for sample size calculation: Critical step for any clinical trials! Saudi J Anaesth. 2016 Sep;10(3):328. Doi: PMid:27375390 PMCid:PMC4916819

Dahiru T, Aliyu A, Kene TS. Statistics in Medical Research: Misuse of Sampling and Sample Size Determination.

Sakpal TV. Sample Size Estimation in Clinical Trial. Perspect Clin Res. 2010;1(2):67-9.

Jones SR, Carley S, Harrison M. An introduction to power and sample size estimation. Emerg Med J. 2003 Sep;20(5):453-8. Doi: PMid:12954688 PMCid:PMC1726174

Chadha V. Sample size determination in health studies. NTI Bulletin. 2006;42(3 & 4):55-62.




How to Cite

Patel D. Sample Size Estimation in Clinical Trials. Natl J Community Med [Internet]. 2024 Jun. 1 [cited 2024 Jun. 23];15(06):503-8. Available from:



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