Abstract

Sample size estimation for a research study is the most crucial part of the research process because it helps to produce reliable results which improve generalizability of study results. A researcher must have understanding about significance level, effect size, study’s power, and effect size; margin of error and ratio in event among population and design effect to use sample size calculation formulas efficiently. There are different formulas of sample size calculation for different types of variables measured in distinct study designs, namely descriptive, epidemiological, comparative, and interventional research studies which are covered in this article. Review authors searched online and grey literature related to sample size and read extensively. There were two authors who extracted and complied information related to topic.

Key words: Sample Size Calculation; Observational Studies; Experimental Studies; Case–Control and Cohort Studies