The most frequently asked question to a statistician: The sample size

Mult Scler. 2017 Apr;23(5):644-646. doi: 10.1177/1352458517695471. Epub 2017 Feb 1.


The calculation of the sample size needed for a clinical study is the challenge most frequently put to statisticians, and it is one of the most relevant issues in the study design. The correct size of the study sample optimizes the number of patients needed to get the result, that is, to detect the minimum treatment effect that is clinically relevant. Minimizing the sample size of a study has the advantage of reducing costs, enhancing feasibility, and also has ethical implications. In this brief report, I will explore the main concepts on which the sample size calculation is based.

Keywords: Sample size; clinical trials; power.

Publication types

  • Review

MeSH terms

  • Clinical Trials as Topic*
  • Humans
  • Research Design*
  • Research Personnel*
  • Sample Size*
  • Statistics as Topic