विधियों की तुलना करें

	पारिस्थितिक अध्ययन	समूह अध्ययन
क्षेत्र	महामारी विज्ञान	महामारी विज्ञान
परिवार	Process / pipeline	Process / pipeline
उद्भव वर्ष	19th century (Snow 1854); formalised mid-20th century	Mid-20th century (formal epidemiological design codified ~1950s)
प्रवर्तक	Various; foundational work by John Snow (1854) and systematised in modern form by Brian MacMahon and colleagues	Doll & Hill (British Doctors Study, 1951); Snow (cholera, 1854)
प्रकार	Observational epidemiological study	Observational longitudinal study design
मौलिक स्रोत	Morgenstern, H. (1995). Ecologic studies in epidemiology: concepts, principles, and methods. Annual Review of Public Health, 16(1), 61–81.	Rothman, K. J., Greenland, S., & Lash, T. L. (2008). Modern Epidemiology (3rd ed.). Lippincott Williams & Wilkins. ISBN: 978-0781755641
उपनाम	aggregate study, correlational study, ecological correlation study, population-level study	longitudinal study, follow-up study, panel study, incidence study
संबंधित	5	6
सारांश	An ecological study is an observational epidemiological design in which the unit of analysis is a group or population — a country, region, city, or time period — rather than an individual. Exposures and outcomes are measured as aggregates (rates, proportions, or means) and then correlated across groups to generate or evaluate hypotheses about population-level associations between risk factors and disease.	A cohort study assembles a group of individuals who share a common starting point — typically freedom from the outcome of interest — and follows them over time to observe who develops the outcome. By comparing incidence rates between exposed and unexposed subgroups, researchers can estimate relative risk and absolute risk differences. Cohort studies are the gold-standard observational design for measuring disease incidence and establishing temporal relationships between exposure and outcome.