Two brothers played with their cousin. One brother later became quite ill, whereas the other did not. Which provides the best explanation for this occurrence?

Correct Answer: C

Rationale: Assuming the two brothers lived in the same household, the environment and the agent or infectious organisms are the same. The only difference could be between the two brothers themselves and their genetic inheritance.

Correct Answer: B

Rationale: The person-place-time model suggests epidemiologists examine demographic characteristics of the community (person characteristics), geographic or environmental factors (place), and common time factors (time - or when the disease struck). Disease characteristics and health protection measures taken are not explicitly part of this model, though they may be considered in other contexts.

Correct Answer: D

Rationale: Confounding occurs when a third factor affects exposure and outcome. In nutritional epidemiology, dietary components (e.g., fat and calories) are correlated (D), complicating isolation of effects (e.g., does fat or total energy increase heart disease risk?). A and B are measurement issues, not confounding. C is false; methods like multivariable adjustment exist.

Correct Answer: A

Rationale: Relative risk (A) measures association (e.g., risk ratio in cohorts). Prevalence (B) and incidence (C) are frequencies, mortality rate (D) is deaths, not associations.

Correct Answer: A

Rationale: An epidemic curve (A) plots cases over time to show outbreak patterns (e.g., point source). B, C, and D are unrelated.