Required sample size for comparing two independent means
- Authors: Grjibovski A.M.1,2, Gorbatova M.A.1, Narkevich A.N.3, Vinogradov K.A.3
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Affiliations:
- Northern State Medical University
- North-Eastern Federal University
- Рrofessor V. F. Voyno-Yasenetsky Krasnoyarsk State Medical University
- Issue: Vol 6, No 2 (2020)
- Pages: 106-113
- Section: RESEARCH METHODOLOGY
- URL: https://seamed.bmoc-spb.ru/jour/article/view/356
- DOI: https://doi.org/10.22328/2413-5747-2020-6-2-106-113
- ID: 356
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Abstract
Sample size calculation in a planning phase is still uncommon in Russian research practice. This situation threatens validity of the conclusions and may introduce Type I error when the false null hypothesis is accepted due to lack of statistical power to detect the existing difference between the means. Comparing two means using unpaired Students’ ttests is the most common statistical procedure in the Russian biomedical literature. However, calculations of the minimal required sample size or retrospective calculation of the statistical power were observed only in very few publications. In this paper we demonstrate how to calculate required sample size for comparing means in unpaired samples using WinPepi and Stata software. In addition, we produced tables for minimal required sample size for studies when two means have to be compared and body mass index and blood pressure are the variables of interest. The tables were constructed for unpaired samples for different levels of statistical power and standard deviations obtained from the literature.
Keywords
About the authors
A. M. Grjibovski
Northern State Medical University;North-Eastern Federal University
Author for correspondence.
Email: Andrej.Grjibovski@gmail.com
ORCID iD: 0000-0002-5464-0498
Andrej M. Grjibovski
Arkhangelsk
Russian FederationM. A. Gorbatova
Northern State Medical University
Email: marigora@mail.ru
ORCID iD: 0000-0002-6363-9595
Maria A. Gorbatova
Arkhangelsk
Russian FederationA. N. Narkevich
Рrofessor V. F. Voyno-Yasenetsky Krasnoyarsk State Medical University
Email: narkevichart@gmail.com
ORCID iD: 0000-0002-1489-5058
Artem N. Narkevich
Krasnoyarsk
Russian FederationK. A. Vinogradov
Рrofessor V. F. Voyno-Yasenetsky Krasnoyarsk State Medical University
Email: vinogradov16@yandex.ru
ORCID iD: 0000-0001-6224-5618
Konstantin A. Vinogradov
Krasnoyarsk
Russian FederationReferences
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