What type of bias is introduced by differential recall of past exposures by cases and controls?

Correct Answer: C

Rationale: Recall bias (C) occurs when cases recall exposures differently than controls (e.g., cancer patients over-reporting). A is selection, B is broad, D is confounding.

Correct Answer: B

Rationale: ROC curves (B) plot sensitivity vs. 1-specificity to assess discrimination (e.g., test accuracy). A, C, and D are unrelated.

Correct Answer: C

Rationale: Lower cutoff (C) increases sensitivity (more positives) but decreases specificity (more false positives). A, B, and D defy trade-off.

Correct Answer: A

Rationale: Case fatality rate (A) is deaths among cases (e.g., 10% for Ebola). B is incidence, C is mortality, D is at-risk.

Correct Answer: C

Rationale: Dose-response (C) shows risk rising with exposure (e.g., more smoking, more cancer). A, B, and D misinterpret.