Sample Size Estimation

Sample size estimation is a critical statistical analytic tool that is necessary for conducting research. The formula for sample size depends on the type of the study. In a cross-sectional study, the formula for sample size is a one-sample prevalence test formula. In a case–control study, the sample size is applied to estimate the odds ratio (OR). Similarly, the sample size for a prospective cohort study is estimated for relation risk. In this chapter, the readers will find basic information for Type I and Type II errors, confidence, power, effect size, and attrition rates. Then they will learn about methods of sample size estimation for the following: cross-sectional study, case–control study, cohort study, and randomized controlled trials (RCTs), with practical examples. The use of a free statistical software, G*Power, is demonstrated.