Why is a cohort design more efficient than a case-control design to study a rare exposure? (Select one best answer) Group of answer choices a. Subjects are selected based on their exposure status. b. Subjects are selected based on their disease status. c. Subjects are selected based on their exposure and disease status. d. Subjects are selected based on their random allocation to treatment or placebo. e. None of these.
A prospective study is a study in which a group of disease-free individuals is identified at one point in time and are followed over a period of time until some of them develop the disease. The development of disease over time is then related to other variables measured at baseline, generally called as exposure variables. The study population in a prospective study is often called a cohort. Thus, another name for this type of study is a cohort study.
A case–control study is a study in which two groups of individuals are initially identified: a group that has the disease under study (the cases) and a group that does not have the disease under study (the controls). An attempt is then made to relate their prior health habits to their current disease status. This type of study is also sometimes called a retrospective study.
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