Indian Journal of Anaesthesia

: 2016  |  Volume : 60  |  Issue : 9  |  Page : 652--656

Sample size calculation: Basic principles

Sabyasachi Das1, Koel Mitra1, Mohanchandra Mandal2 
1 Department of Anaesthesiology and Critical Care, Medical College, Kolkata, West Bengal, India
2 Department of Anaesthesiology and Critical Care, North Bengal Medical College, Sushrutanagar, Darjeeling, West Bengal, India

Correspondence Address:
Sabyasachi Das
107/4A, North Purbachal, Kalitala, Kolkata - 700 078, West Bengal

Addressing a sample size is a practical issue that has to be solved during planning and designing stage of the study. The aim of any clinical research is to detect the actual difference between two groups (power) and to provide an estimate of the difference with a reasonable accuracy (precision). Hence, researchers should do a priori estimate of sample size well ahead, before conducting the study. Post hoc sample size computation is not encouraged conventionally. Adequate sample size minimizes the random error or in other words, lessens something happening by chance. Too small a sample may fail to answer the research question and can be of questionable validity or provide an imprecise answer while too large a sample may answer the question but is resource-intensive and also may be unethical. More transparency in the calculation of sample size is required so that it can be justified and replicated while reporting.

How to cite this article:
Das S, Mitra K, Mandal M. Sample size calculation: Basic principles.Indian J Anaesth 2016;60:652-656

How to cite this URL:
Das S, Mitra K, Mandal M. Sample size calculation: Basic principles. Indian J Anaesth [serial online] 2016 [cited 2020 Sep 19 ];60:652-656
Available from:;year=2016;volume=60;issue=9;spage=652;epage=656;aulast=Das;type=0