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. 2014 Jul-Aug;19(4):27-9.
doi: 10.1590/2176-9451.19.4.027-029.ebo.

How sample size influences research outcomes

Jorge Faber, Lilian Martins Fonseca

How sample size influences research outcomes

Jorge Faber et al. Dental Press J Orthod. 2014 Jul-Aug.

Abstract
in English, Portuguese

Sample size calculation is part of the early stages of conducting an epidemiological, clinical or laboratory study. In preparing a scientific paper, there are ethical and methodological indications for its use. Two investigations conducted with the same methodology and achieving equivalent results, but different only in terms of sample size, may point the researcher in different directions when it comes to making clinical decisions. Therefore, ideally, samples should not be small and, contrary to what one might think, should not be excessive. The aim of this paper is to discuss in clinical language the main implications of the sample size when interpreting a study.

O cálculo amostral faz parte dos estágios iniciais de realização de um estudo epidemiológico, clínico ou laboratorial. Há indicações éticas e metodológicas para o seu emprego na elaboração de um trabalho científico. Duas pesquisas, realizadas com a mesma metodologia obtendo resultados equivalentes, e que diferem apenas no tamanho da amostra, podem apontar para diferentes direções no processo de tomada de decisão clínica. Portanto, as amostras estudadas idealmente não devem ser pequenas e, ao contrário do que pode-se pensar, não devem ser excessivas. O objetivo desse artigo é discutir, numa linguagem clínica, as principais implicações do tamanho das amostras na interpretação de um estudo.

Keywords: Clinical trial; Methodology; Sample calculation; Sample size; Scientific evidence.

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