A review article contributed to the special series on “Research Methodology” in Astrocyte.
Study design forms a core component of research, mainly determined by the study objectives, and it in turn further decides the type of statistical analyses to be carried out. Observational studies are devoid of the investigator’s control over assignment of a subject to the treated or control group, in contrast to interventional studies Even though randomized controlled trials are seen as the best study design, evidence shows that properly conducted observational studies give similar results, and is relevant in medical research where ethics and feasibility concerns assume great significance. Observational studies point out towards possible causal associations, are less resource intensive than trials and have a better external validity. This review article discusses various types of observational study designs such as case reports, cross sectional, cohort, case-control and nested case-control studies with real literature examples.
Keywords: Case control, case series, cohort, ecologic, nested case control, observational study