This topic is taught through its practice: 12 practice questions, each with the reasoning behind the answer, and the same idea again in plain words.
Quick check
5 questions here, of 12 in this lesson’s practice set. Answers stay hidden until you check.
Question 1 of 5foundational
A researcher enrolls 120 volunteers and places them evenly into two study groups: one group receives a new relaxation program and the other receives the usual study-skills session. Which statement best describes the defining feature of an experimental study design?
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Question 2 of 5foundational
Investigators enroll 800 nurses, collect dietary information in 4 waves spaced 2 years apart, and record who develops hypertension over the full follow-up period. Which feature makes this an observational study rather than an experimental one?
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Question 3 of 5foundational
A team identifies 60 patients who developed a surgical wound infection and 180 comparable patients who did not, then reviews earlier records of both groups for possible exposures. Which term names this design?
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Question 4 of 5intermediate
What is the primary purpose of random assignment in a trial that randomizes 200 participants in a 1:1 ratio to an intervention group or a control group?
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Question 5 of 5intermediate
A cohort study enrolls exposed and unexposed workers in 2020 and follows them for 5 years, while a case-control study of the same research question is run separately. Which comparison of the two designs is accurate?
