Nokea
Identify the type of study design described: Questionnaires were mailed to every 10th person listed in the city telephone directory. Each person was asked to provide his or her age, sex, and smoking habits and to describe the presence of any respiratory symptoms during the preceding 7 days.
- A. Cohort study
- B. Case-control study
- C. Cross-sectional study
- D. Ecological study
Correct Answer: C
Rationale: This survey-based approach is characteristic of a cross-sectional study.
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Why is the availability of a reliable and safe water source a concern to officials in the United States and the rest of the world?
- A. Waterborne diseases, scarcity issues.
- B. Abundant freshwater reserves globally.
- C. Low demand for clean water.
- D. Complete reliance on desalination.
Correct Answer: A
Rationale: Access to safe water prevents waterborne diseases and addresses growing scarcity concerns worldwide.
The best estimate of the association between wedding cake and illness is:
- A. 6.1
- B. 7.7
- C. 68.4
- D. 83.7
Correct Answer: B
Rationale: Calculated odds ratio reflects the strength of association.
Selection bias interferes-
- A. internal validity
- B. external validity
- C. face validity
- D. all
Correct Answer: A
Rationale: Selection bias undermines internal validity by affecting the comparability of study groups.
The LD50 of highly toxic substance is.... mg/ kg.
- A. less than 1
- B. Jan-50
- C. 51-500
- D. 50-500
Correct Answer: A
Rationale: Highly toxic substances have an LD50 value of less than 1 mg/kg, indicating extreme toxicity.
What do vital statistics provide important sources of data on?
- A. Morbidity.
- B. Mortality.
- C. Health-related behaviors.
- D. Injury and disability.
Correct Answer: D
Rationale: Vital statistics also track injuries and disabilities, contributing to a comprehensive health overview.