Study Designs in Clinical Research

Background: The quality of scientific literature is judged by study design, validity, and applicability to unique patient populations. Methods: We searched the available literature to explore the hierarchy of evidence, explain research fundamentals such as sample size calculation, and discuss common study designs employed in surgical research and the interpretation of trial designs. Results: Each unique study design has restraints created by some degree of systematic errors and bias. This article provides definitions for the scientific boundaries of case control, retrospective, before-and-after, prospective observational, randomized controlled designs, and meta-analyses. Conclusion: Critical thinking and appraisal of the literature is a skill that requires lifelong training and practice. Clinical research education and design need to garner more attention in the medical community.