ABSTRACT
The aim of this review is to: i) stress the effect of sample size and power analysis on study results, ii) construct information to guide researchers on the components that should be taken into consideration in order to calculate the sample size. The components which effect sample size calculation with power analysis in clinical trials are type I error (α), type II error (β), difference between the groups or effect size, allocation ratio and direction of study hypothesis (one/two sided). Sample size calculation with power analysis in the planning stage of clinical trials guarantees the reliability of the study results, in addition to preventing source extravagance.
Keywords:
Power analysis, sample size, type I error, type II error, effect size