Following are true about coho study, except:
**Core Concept**
A cohort study is a type of observational study where a group of individuals (cohort) is followed over time to assess the development of outcomes or diseases. This study design is used to investigate the relationship between exposure and outcome, and it can be prospective or retrospective.
**Why the Correct Answer is Right**
Cohort studies are particularly useful for studying rare outcomes or diseases, as they allow for the collection of data over an extended period. They can also provide valuable information on the natural history of a disease and the impact of various risk factors. In a cohort study, the exposure is typically assessed before the outcome occurs, and this temporal relationship is essential for establishing causality.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because cohort studies can be prospective or retrospective, and they are not limited to a specific study design.
**Option B:** This option is incorrect because cohort studies are often used to study the development of outcomes or diseases over time, and they can provide valuable information on the natural history of a disease.
**Option C:** This option is incorrect because cohort studies are observational, meaning they do not involve any manipulation of the study population or intervention. They are used to study the relationship between exposure and outcome in a natural setting.
**Clinical Pearl / High-Yield Fact**
A key advantage of cohort studies is that they can provide valuable information on the temporal relationship between exposure and outcome, which is essential for establishing causality. This is in contrast to case-control studies, which can be subject to recall bias and other limitations.
**Correct Answer: None of the above.**