NR 503 / NR503 Midterm Exam Actual Exam 2026 |
Population Health Epidemiology & Biostatistics |
Questions with Verified Answers | 100% Correct | Pass
Guaranteed
SECTION 1: Epidemiological Concepts & Measures
Q1: Which of the following best describes the difference between incidence and
prevalence?
A. Incidence measures existing cases; prevalence measures new cases
B. Incidence measures new cases; prevalence measures existing cases
C. Both measure existing cases but prevalence includes mortality
D. Both measure new cases but incidence adjusts for age
Correct Answer: B
Rationale: Incidence quantifies the rate at which new cases of a disease occur in a
population at risk over a specified time, whereas prevalence measures the proportion of
existing cases (old + new) at a point or period. Option A reverses the definitions; C and
D incorrectly state both measure the same metric.
Q2: A county health department reports 45 new cases of influenza in a population of
15,000 during January 2026. The incidence rate per 1,000 person-years is:
A. 1.5
B. 3.0
,C. 4.5
D. 15
Correct Answer: B
Rationale: Incidence rate = (45 new cases / 15,000 pop) × 1,000 = 3.0 per 1,000. Option
A understates; C and D miscalculate the multiplier or decimal placement.
Q3: In a cohort study, the calculated relative risk (RR) is 0.75. The most accurate
interpretation is:
A. 75% increase in risk among exposed
B. 25% reduction in risk among exposed
C. No association between exposure and outcome
D. 75% of the exposed will develop the outcome
Correct Answer: B
Rationale: RR = 0.75 means the exposed group has 25% lower risk (1 – 0.75 = 0.25). An
RR >1 indicates increased risk; =1 means no association; D incorrectly converts RR to
absolute probability.
Q4: Which measure is most appropriate to compare mortality rates between two
populations with different age structures?
A. Crude mortality rate
B. Age-specific mortality rate
C. Age-adjusted (standardized) mortality rate
D. Case-fatality rate
, Correct Answer: C
Rationale: Age-adjusted rates remove the confounding effect of differing age
distributions, allowing fair comparisons. Crude rates (A) are distorted; age-specific (B)
is useful but not comparative overall; case-fatality (D) is prognosis, not population
comparison.
Q5: The attack rate during an outbreak is calculated as:
A. (Deaths ÷ Total population) × 100
B. (New cases ÷ Population at risk) × 100
C. (Total cases ÷ Total population) × 1,000
D. (Recovered cases ÷ Total cases) × 100
Correct Answer: B
Rationale: Attack rate = (new cases / population at risk) × multiplier during a defined
outbreak period. Option A is a mortality measure; C uses total population and wrong
multiplier; D is recovery proportion.
Q6: A point prevalence survey finds 120 existing cases of diabetes in a population of
3,000. The point prevalence per 1,000 persons is:
A. 20
B. 30
C. 40
D. 60
Correct Answer: C
Population Health Epidemiology & Biostatistics |
Questions with Verified Answers | 100% Correct | Pass
Guaranteed
SECTION 1: Epidemiological Concepts & Measures
Q1: Which of the following best describes the difference between incidence and
prevalence?
A. Incidence measures existing cases; prevalence measures new cases
B. Incidence measures new cases; prevalence measures existing cases
C. Both measure existing cases but prevalence includes mortality
D. Both measure new cases but incidence adjusts for age
Correct Answer: B
Rationale: Incidence quantifies the rate at which new cases of a disease occur in a
population at risk over a specified time, whereas prevalence measures the proportion of
existing cases (old + new) at a point or period. Option A reverses the definitions; C and
D incorrectly state both measure the same metric.
Q2: A county health department reports 45 new cases of influenza in a population of
15,000 during January 2026. The incidence rate per 1,000 person-years is:
A. 1.5
B. 3.0
,C. 4.5
D. 15
Correct Answer: B
Rationale: Incidence rate = (45 new cases / 15,000 pop) × 1,000 = 3.0 per 1,000. Option
A understates; C and D miscalculate the multiplier or decimal placement.
Q3: In a cohort study, the calculated relative risk (RR) is 0.75. The most accurate
interpretation is:
A. 75% increase in risk among exposed
B. 25% reduction in risk among exposed
C. No association between exposure and outcome
D. 75% of the exposed will develop the outcome
Correct Answer: B
Rationale: RR = 0.75 means the exposed group has 25% lower risk (1 – 0.75 = 0.25). An
RR >1 indicates increased risk; =1 means no association; D incorrectly converts RR to
absolute probability.
Q4: Which measure is most appropriate to compare mortality rates between two
populations with different age structures?
A. Crude mortality rate
B. Age-specific mortality rate
C. Age-adjusted (standardized) mortality rate
D. Case-fatality rate
, Correct Answer: C
Rationale: Age-adjusted rates remove the confounding effect of differing age
distributions, allowing fair comparisons. Crude rates (A) are distorted; age-specific (B)
is useful but not comparative overall; case-fatality (D) is prognosis, not population
comparison.
Q5: The attack rate during an outbreak is calculated as:
A. (Deaths ÷ Total population) × 100
B. (New cases ÷ Population at risk) × 100
C. (Total cases ÷ Total population) × 1,000
D. (Recovered cases ÷ Total cases) × 100
Correct Answer: B
Rationale: Attack rate = (new cases / population at risk) × multiplier during a defined
outbreak period. Option A is a mortality measure; C uses total population and wrong
multiplier; D is recovery proportion.
Q6: A point prevalence survey finds 120 existing cases of diabetes in a population of
3,000. The point prevalence per 1,000 persons is:
A. 20
B. 30
C. 40
D. 60
Correct Answer: C
