Respuesta :

A retrospective study is a type of an observational study that enrolls participants.

What are the difference between experimental and observational studies?

observational studies refers to do survey on a  group of individuals in a real-world setting. It is also known as descriptive studies

Here, the researchers do not intervene with the study group. They do not  make any predictions of the causality rather than only look at correlations.

In experimental studies  researchers  intervene , for instance, a study of a drug, and its effects on a group of individuals.

For more details regarding observational study , visit:

https://brainly.com/question/17593565

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Your question was incomplete. So the probable question is

What type of study is characterized by large numbers of subjects, all healthy at the time the study begins, being questioned regarding their exposures?

A. Interventional

B. cohort

C. retrospective

D. prospective