A myriad Of methods: Calculated sample size for two proportions was dependent on the choice of sample size formula and software

摘要

Objectives: Several methods exist to calculate sample size for the difference of proportions (risk difference). Researchers are often unaware that there are different formulae, different underlying assumptions, and what the impact of choice of formula is on the calculated sample size. The aim of this study was to discuss and compare different sample size formulae for the risk difference.