PRACTICAL ASPECTS FOR THE CALCULATION OF SAMPLE SIZE IN OBSERVATIONAL STUDIES

Soto A. · Revista de la Facultad de Medicina Humana (2026) · DOI: 10.25176/rfmh.v26i3.8503

Resumen

Observational studies are an important source of information in clinical epidemiology, but sample size calculation often poses difficulties during research planning. This calculation should be consistent with the study objective, study design, and effect measure of interest, as an inappropriate choice may lead to imprecise estimates or inefficient use of available resources. This methodological review presents the concepts and parameters required to estimate sample size or, when appropriate, statistical power in descriptive and analytical observational studies, including cross-sectional, case-control, and cohort designs. Alpha and beta errors, precision, confidence level, baseline outcome frequency, expected effect size, and selection of the association measure according to study design are reviewed. Considerations for finite populations, adjustments for loss to follow-up or incomplete data, and scenarios in which the number of observations is predetermined are also described; in such cases, statistical power or the minimum detectable effect may be assessed. Finally, recommendations are provided for documenting sample size calculations in research protocols and for selecting statistical tools according to the characteristics of the study. © Artículo publicado por la Revista de la Facultad de Medicina Humana de la Universidad Ricardo Palma. Es un artículo de acceso abierto, distribuido bajo los términos de la Licencia Creative Commons: Creative Commons Attribution 4.0 International, CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), que permite el uso no comercial, distribución y reproducción en cualquier medio, siempre que la obra original sea debidamente citada. Para uso comercial, por favor póngase en contacto con revista.medicina@urp.pe.

Instituciones: Universidad Ricardo Palma