השוואת שיטות

	מבנה מחקר עוקבה	תכנון מחקר חתך
תחום	מחקר קליני	מחקר קליני
משפחה	Process / pipeline	Process / pipeline
שנת המקור	1970s-1980s	1950s-1970s
הוגה השיטה	Donald Acheson, Olli Miettinen, and others in modern epidemiology	Epidemiologists in the mid-20th century; formalized by Kelsey, Rothman, and others
סוג	Research Design	Research Design
מקור מכונן	Miettinen, O. S. (1976). Estimability and estimation in case-referent studies. American Journal of Epidemiology, 103(2), 226–235.	Kelsey, J. L., Whittemore, A. S., Evans, A. S., & Thompson, W. D. (1996). Methods in Observational Epidemiology (2nd ed.). Oxford University Press. ISBN: 978-0195083299
כינויים	prospective study, follow-up study, longitudinal study, cohort study	prevalence study, cross-sectional survey, snapshot study, survey design
קשורות	2	2
תקציר	A cohort study follows a group of individuals forward in time from exposure to outcome. Exposed and unexposed participants (or participants with differing exposure levels) are enrolled at baseline, characterized, and observed prospectively until the outcome occurs or the study ends. Cohort studies are fundamental to epidemiology and are the design of choice for establishing causal associations when randomized trials are infeasible or unethical.	A cross-sectional study (or prevalence study) measures exposure and outcome simultaneously at a single point in time, producing a 'snapshot' of a population. Respondents are recruited and surveyed (or examined) on the same occasion, capturing current prevalence of both exposure and disease. Cross-sectional studies are simple, quick, and inexpensive, making them popular for needs assessments, surveillance, and generating hypotheses—though they cannot establish causality due to lack of temporal sequence.