[How to estimate the sample size in special conditions? [part two]]

ABSTRACT

In the previous paper, the basic concepts of sample size calculation were presented. This paper explores main post-calculation adjustments of the sample size calculation in special circumstances such as multiple group comparisons, unbalanced studies [with unequal number of subjects in different groups]; sample size correction for missing data, and adjustment for finite population size. In addition, the concept of design effect in multi-stage sampling and its impact on the sample size are presented. We then focused on the sample size estimation when we have to use non-parametric statistical tests for data analysis. The concept of power-efficacy of parametric versus non-parametric methods and its use in the correction of sample size has been explained