Common medical and statistical problems

• Autor(a) principal: Oliveira, M. Rosário
• Data de Publicação: 2020
• Outros Autores: Subtil, Ana, Gonçalves, Luzia
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/116610
• topic: Conditional probability; Coverage probability; Sample size; Sensitivity; Specificity; Applied Mathematics

Sample size calculation in biomedical practice is typically based on the problematicWald method for a binomial proportion, with potentially dangerous consequences. This work highlights the need of incorporating the concept of conditional probability in sample size determination to avoid reduced sample sizes that lead to inadequate confidence intervals. Therefore, new definitions are proposed for coverage probability and expected length of confidence intervals for conditional probabilities, like sensitivity and specificity. The new definitions were used to assess seven confidence interval estimation methods. In order to determine the sample size, two procedures-an optimal one, based on the new definitions, and an approximation-were developed for each estimation method. Our findings confirm the similarity of the approximated sample sizes to the optimal ones. R code is provided to disseminate these methodological advances and translate them into biomedical practice.