This figure depicts types of epidemiological studies in a hierarchy.

The weight of evidence for causality increases with the height or level on the figure. The highest study is “Controlled human exposure” within a box labeling it as the only experimental study type.

The other study designs are contained within a box labeling observational studies. They are further divided into analytic and descriptive types with the analytic designs above the descriptive designs in the hierarchy. Two analytic studies types are shown to be (listed from most weight of evidence to least) longitudinal and cross-sectional. Two sub-categories of longitudinal study designs are mentioned (listed from most weight of evidence to least): cohort and case-control.

Three descriptive study designs are given (from most weight of evidence to least): ecologic, case series, and case report.

	This work is in the public domain in the United States because it is a work prepared by an officer or employee of the United States Government as part of that person’s official duties under the terms of Title 17, Chapter 1, Section 105 of the US Code. Note: This only applies to original works of the Federal Government and not to the work of any individual U.S. state, territory, commonwealth, county, municipality, or any other subdivision. This template also does not apply to postage stamp designs published by the United States Postal Service since 1978. (See § 313.6(C)(1) of Compendium of U.S. Copyright Office Practices). It also does not apply to certain US coins; see The US Mint Terms of Use.
This file has been identified as being free of known restrictions under copyright law, including all related and neighboring rights.

https://creativecommons.org/publicdomain/mark/1.0/PDMCreative Commons Public Domain Mark 1.0falsefalse

This media file is uncategorized. Please help improve this media file by adding it to one or more categories, so it may be associated with related media files (how?), and so that it can be more easily found. Please notify the uploader with {{subst:Please link images|File:Epidemiologic study hierarchy.png}} ~~~~