Related Experiment Video
Updated: May 20, 2026

Inverse Probability of Treatment Weighting (Propensity Score) using the Military Health System Data Repository and National Death Index
Published on: January 8, 2020
Observational studies in the era of randomized trials: finding the balance
Renan C Castillo1, Daniel O Scharfstein, Ellen J MacKenzie
1Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, 624 North Broadway Street, HH543, Baltimore, MD 21205, USA.
Abstract:
Randomized controlled trials (RCTs) constitute the gold standard for the generation of evidence-based medicine, but may not always be feasible. Furthermore, randomization alone does not guarantee the utility of the research, as evidenced by thousands of uninformative RCTs documented in the literature. Observational studies, including longitudinal, retrospective, and case-control designs, can contribute to the body of evidence in meaningful ways, provide useful information when an RCT is unethical or not feasible, generate hypotheses for RCTs, or provide preliminary work to better inform design of future RCTs. They can also be used to study rare outcomes, risk factors, and side effects, and to examine whether results from RCTs translate into effective treatment in routine practice. Use of modern statistical techniques, both in the study design and in the analysis stage, can improve the usefulness of the evidence obtained from observational studies.
Related Concept Videos
Observational Studies
There are three types of observational studies – Prospective, retrospective, and cross-sectional.
Prospective Study
Prospective studies, also known as longitudinal or cohort studies, are carried out by collecting future data from groups sharing similar characteristics. One example of...
Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
Regression Toward the Mean
Bias in Epidemiological Studies
Naturalistic Observations
Bioequivalence Experimental Study Designs: Completely Randomized and Randomized Block Designs
