title: Sample size calculation: Basic principles.
abstract: 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 doa prioriestimate of sample size well ahead, before conducting the study.Post hocsample 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.
authors.affiliation: Department of Anaesthesiology and Critical Care, Medical College, Kolkata, West Bengal, India.
authors.forename: Sabyasachi
authors.initials: S
authors.lastname: Das
authors.affiliation: Department of Anaesthesiology and Critical Care, Medical College, Kolkata, West Bengal, India.
authors.forename: Koel
authors.initials: K
authors.lastname: Mitra
authors.affiliation: Department of Anaesthesiology and Critical Care, North Bengal Medical College, Sushrutanagar, Darjeeling, West Bengal, India.
authors.forename: Mohanchandra
authors.initials: M
authors.lastname: Mandal
keywords: Effect size; medical research; power; randomized control trial; research hypothesis; sample size; study design