On the basis of findings related to elevated blood levels of cholesterol, a researcher wanted to determine whether a new drug would notably lower the blood levels of cholesterol in otherwise healthy persons. Which study would the researcher most likely use?

Correct Answer: B

Rationale: Experimental design is used to test treatment and prevention strategies. Subjects are randomly assigned to the experimental group to obtain the new drug while the control group receives a placebo or alternative. The changes in blood cholesterol level would then be measured. A cross-sectional study examines relationships between potential causal factors and disease at a specific time. A prospective study monitors a group of disease-free individuals to determine if and when disease occurs. A retrospective study compares individuals with a particular condition or disease with those who do not have the disease.

Correct Answer: C

Rationale: A pandemic (C) is a global outbreak (e.g., 1918 flu). Endemic (A) is constant presence, epidemic (B) is regional excess, and cluster (D) is a localized group.

Correct Answer: C

Rationale: Relative risk (C) is the ratio of disease incidence in exposed vs. unexposed, reflecting risk among exposed. A is total cases, B is new cases, D is excess risk.

Correct Answer: A

Rationale: Incidence rate (A) measures new cases over time. B, C, and D are test performance metrics, not frequency.

Correct Answer: B

Rationale: Cohort studies (B) track groups over time for disease onset (e.g., Framingham). A is case-control, C is cross-sectional, D is RCT.