[Do you want to gain a profound insight into sample size and statistical power?]

ABSTRACT

Sample size estimation is one of the crucial issues in the research methodology in medical sciences. It is an important issue for not only researchers but also readers of medical papers; their frequent questions show how much they need to simple but accurate information. This paper presents the basic concepts of sample size calculation, and simplifies complicated issues using concrete examples to clarify the concept of sample size estimation for none-professional readers in statistics. The paper starts with explaining the basic concepts of sample size calculation such as effect size, confidence interval and confidence coefficient, statistical errors, and assumptions in sample size calculation. Then, it presents the common formulae in the sample size calculation to estimate a mean, a proportion, to compare two means and to compare two proportions