[EPIDEMIOLOGY MIDTERM I EXAM] QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2026 Q&A | INSTANT DOWNLOAD PDF
CORE DOMAINS
Principles of Epidemiology and Study Design
Measures of Disease Frequency and Association
Infectious Disease Epidemiology and Outbreak Investigation
Chronic Disease Epidemiology and Risk Factors
Biostatistics and Data Interpretation in Epidemiology
Screening, Surveillance, and Public Health Practice
Regulatory, Legal, and Ethical Standards in Epidemiologic Research
Applied Epidemiology and Real-World Decision Making
INTRODUCTION
The Epidemiology Midterm I Examination assesses foundational and applied competencies required
for professional practice in public health and clinical epidemiology. It evaluates knowledge of study
design, disease measurement, outbreak investigation, surveillance, biostatistical interpretation, and
ethical and legal standards. The exam uses multiple-choice and scenario-based questions to test
critical thinking, data interpretation, and real-world decision-making. Candidates must demonstrate
the ability to apply epidemiologic principles to complex public health problems, evaluate evidence,
and select defensible courses of action consistent with regulatory and professional expectations.
SECTION ONE: QUESTIONS 1–300
1. Which measure best describes the proportion of a population that has a disease at a specific
point in time?
A. Incidence rate
B. Point prevalence
C. Attack rate
D. Case fatality rate
✔ B. Point prevalence
RATIONALE: Point prevalence measures the proportion of existing cases in a population at a single
point in time.
2. In an outbreak investigation, the first step is usually to:
A. Implement control measures
B. Verify the diagnosis
C. Establish the existence of an outbreak
D. Perform analytic epidemiology
✔ C. Establish the existence of an outbreak
RATIONALE: Confirming that observed cases exceed expected levels is the essential first step before
further investigation.
3. Which study design is most appropriate for studying rare exposures?
A. Cohort study
, B. Case-control study
C. Cross-sectional study
D. Ecologic study
✔ B. Case-control study
RATIONALE: Case-control studies efficiently sample based on outcome and are useful for rare
exposures when cases are available.
4. The attributable risk percent represents:
A. The proportion of disease in the exposed attributable to the exposure
B. The ratio of incidence in exposed to unexposed
C. The prevalence of exposure in cases
D. The overall incidence in the population
✔ A. The proportion of disease in the exposed attributable to the exposure
RATIONALE: Attributable risk percent quantifies the fraction of disease among the exposed that
would be eliminated if exposure were removed.
5. Which of the following is a legal requirement for protecting human subjects in epidemiologic
research?
A. Informed consent
B. Randomization
C. Blinding
D. Matching
✔ A. Informed consent
RATIONALE: Informed consent is a foundational legal and ethical requirement for research involving
human subjects.
6. A sudden increase in cases of a disease above expected levels in a defined population is called:
A. Endemic
B. Epidemic
C. Pandemic
D. Sporadic
✔ B. Epidemic
RATIONALE: An epidemic is the occurrence of disease cases above normal expectancy in a
population or area.
7. Which measure of association is calculated in a cohort study?
A. Odds ratio
B. Relative risk
C. Prevalence ratio
D. Correlation coefficient
✔ B. Relative risk
RATIONALE: Cohort studies allow direct calculation of incidence and therefore relative risk.
, 8. Selection bias in a case-control study most commonly arises from:
A. Differential recall of exposure
B. Nonrandom selection of cases or controls
C. Loss to follow-up
D. Measurement error in exposure
✔ B. Nonrandom selection of cases or controls
RATIONALE: Selection bias occurs when cases or controls are not representative of the source
population.
9. Which of the following is an example of a notifiable disease?
A. Common cold
B. Measles
C. Seasonal allergies
D. Hypertension
✔ B. Measles
RATIONALE: Measles is a nationally notifiable disease requiring prompt reporting to public health
authorities.
10. The primary purpose of public health surveillance is to:
A. Diagnose individual patients
B. Monitor trends and guide interventions
C. Conduct clinical trials
D. Determine insurance reimbursement
✔ B. Monitor trends and guide interventions
RATIONALE: Surveillance systematically collects and analyzes health data to inform public health
action.
11. A test with high sensitivity will:
A. Rarely miss true cases
B. Rarely misclassify healthy people
C. Have high positive predictive value
D. Have high specificity
✔ A. Rarely miss true cases
RATIONALE: Sensitivity is the ability of a test to correctly identify those with disease.
12. Which of the following is a key feature of a randomized controlled trial?
A. Participants choose their treatment
B. Allocation to groups is random
C. Researchers select who gets treatment
D. There is no control group
✔ B. Allocation to groups is random
RATIONALE: Randomization minimizes confounding by distributing known and unknown factors
evenly.
, 13. The incubation period is:
A. Time from exposure to onset of symptoms
B. Time from onset to recovery
C. Time from diagnosis to death
D. Time from exposure to diagnosis
✔ A. Time from exposure to onset of symptoms
RATIONALE: The incubation period is the interval between exposure and appearance of clinical
signs.
14. Which of the following best defines herd immunity?
A. Immunity acquired through vaccination only
B. Indirect protection of unvaccinated individuals due to high population immunity
C. Immunity from previous infection
D. Genetic resistance to disease
✔ B. Indirect protection of unvaccinated individuals due to high population immunity
RATIONALE: Herd immunity occurs when sufficient immune individuals reduce transmission to
protect others.
15. Which measure is used to compare mortality between populations while adjusting for age?
A. Crude mortality rate
B. Age-adjusted mortality rate
C. Case fatality rate
D. Attack rate
✔ B. Age-adjusted mortality rate
RATIONALE: Age adjustment removes the effect of different age distributions when comparing
mortality.
16. A confounder is a variable that:
A. Is caused by the exposure
B. Is associated with both exposure and outcome
C. Mediates the effect of exposure
D. Is unrelated to outcome
✔ B. Is associated with both exposure and outcome
RATIONALE: A confounder distorts the exposure-outcome relationship and is not on the causal
pathway.
17. Which of the following is an ethical principle in epidemiologic research?
A. Beneficence
B. Randomization
C. Stratification
D. Blinding
✔ A. Beneficence
RATIONALE: Beneficence requires maximizing benefits and minimizing harms in research.
PLUS RATIONALES 2026 Q&A | INSTANT DOWNLOAD PDF
CORE DOMAINS
Principles of Epidemiology and Study Design
Measures of Disease Frequency and Association
Infectious Disease Epidemiology and Outbreak Investigation
Chronic Disease Epidemiology and Risk Factors
Biostatistics and Data Interpretation in Epidemiology
Screening, Surveillance, and Public Health Practice
Regulatory, Legal, and Ethical Standards in Epidemiologic Research
Applied Epidemiology and Real-World Decision Making
INTRODUCTION
The Epidemiology Midterm I Examination assesses foundational and applied competencies required
for professional practice in public health and clinical epidemiology. It evaluates knowledge of study
design, disease measurement, outbreak investigation, surveillance, biostatistical interpretation, and
ethical and legal standards. The exam uses multiple-choice and scenario-based questions to test
critical thinking, data interpretation, and real-world decision-making. Candidates must demonstrate
the ability to apply epidemiologic principles to complex public health problems, evaluate evidence,
and select defensible courses of action consistent with regulatory and professional expectations.
SECTION ONE: QUESTIONS 1–300
1. Which measure best describes the proportion of a population that has a disease at a specific
point in time?
A. Incidence rate
B. Point prevalence
C. Attack rate
D. Case fatality rate
✔ B. Point prevalence
RATIONALE: Point prevalence measures the proportion of existing cases in a population at a single
point in time.
2. In an outbreak investigation, the first step is usually to:
A. Implement control measures
B. Verify the diagnosis
C. Establish the existence of an outbreak
D. Perform analytic epidemiology
✔ C. Establish the existence of an outbreak
RATIONALE: Confirming that observed cases exceed expected levels is the essential first step before
further investigation.
3. Which study design is most appropriate for studying rare exposures?
A. Cohort study
, B. Case-control study
C. Cross-sectional study
D. Ecologic study
✔ B. Case-control study
RATIONALE: Case-control studies efficiently sample based on outcome and are useful for rare
exposures when cases are available.
4. The attributable risk percent represents:
A. The proportion of disease in the exposed attributable to the exposure
B. The ratio of incidence in exposed to unexposed
C. The prevalence of exposure in cases
D. The overall incidence in the population
✔ A. The proportion of disease in the exposed attributable to the exposure
RATIONALE: Attributable risk percent quantifies the fraction of disease among the exposed that
would be eliminated if exposure were removed.
5. Which of the following is a legal requirement for protecting human subjects in epidemiologic
research?
A. Informed consent
B. Randomization
C. Blinding
D. Matching
✔ A. Informed consent
RATIONALE: Informed consent is a foundational legal and ethical requirement for research involving
human subjects.
6. A sudden increase in cases of a disease above expected levels in a defined population is called:
A. Endemic
B. Epidemic
C. Pandemic
D. Sporadic
✔ B. Epidemic
RATIONALE: An epidemic is the occurrence of disease cases above normal expectancy in a
population or area.
7. Which measure of association is calculated in a cohort study?
A. Odds ratio
B. Relative risk
C. Prevalence ratio
D. Correlation coefficient
✔ B. Relative risk
RATIONALE: Cohort studies allow direct calculation of incidence and therefore relative risk.
, 8. Selection bias in a case-control study most commonly arises from:
A. Differential recall of exposure
B. Nonrandom selection of cases or controls
C. Loss to follow-up
D. Measurement error in exposure
✔ B. Nonrandom selection of cases or controls
RATIONALE: Selection bias occurs when cases or controls are not representative of the source
population.
9. Which of the following is an example of a notifiable disease?
A. Common cold
B. Measles
C. Seasonal allergies
D. Hypertension
✔ B. Measles
RATIONALE: Measles is a nationally notifiable disease requiring prompt reporting to public health
authorities.
10. The primary purpose of public health surveillance is to:
A. Diagnose individual patients
B. Monitor trends and guide interventions
C. Conduct clinical trials
D. Determine insurance reimbursement
✔ B. Monitor trends and guide interventions
RATIONALE: Surveillance systematically collects and analyzes health data to inform public health
action.
11. A test with high sensitivity will:
A. Rarely miss true cases
B. Rarely misclassify healthy people
C. Have high positive predictive value
D. Have high specificity
✔ A. Rarely miss true cases
RATIONALE: Sensitivity is the ability of a test to correctly identify those with disease.
12. Which of the following is a key feature of a randomized controlled trial?
A. Participants choose their treatment
B. Allocation to groups is random
C. Researchers select who gets treatment
D. There is no control group
✔ B. Allocation to groups is random
RATIONALE: Randomization minimizes confounding by distributing known and unknown factors
evenly.
, 13. The incubation period is:
A. Time from exposure to onset of symptoms
B. Time from onset to recovery
C. Time from diagnosis to death
D. Time from exposure to diagnosis
✔ A. Time from exposure to onset of symptoms
RATIONALE: The incubation period is the interval between exposure and appearance of clinical
signs.
14. Which of the following best defines herd immunity?
A. Immunity acquired through vaccination only
B. Indirect protection of unvaccinated individuals due to high population immunity
C. Immunity from previous infection
D. Genetic resistance to disease
✔ B. Indirect protection of unvaccinated individuals due to high population immunity
RATIONALE: Herd immunity occurs when sufficient immune individuals reduce transmission to
protect others.
15. Which measure is used to compare mortality between populations while adjusting for age?
A. Crude mortality rate
B. Age-adjusted mortality rate
C. Case fatality rate
D. Attack rate
✔ B. Age-adjusted mortality rate
RATIONALE: Age adjustment removes the effect of different age distributions when comparing
mortality.
16. A confounder is a variable that:
A. Is caused by the exposure
B. Is associated with both exposure and outcome
C. Mediates the effect of exposure
D. Is unrelated to outcome
✔ B. Is associated with both exposure and outcome
RATIONALE: A confounder distorts the exposure-outcome relationship and is not on the causal
pathway.
17. Which of the following is an ethical principle in epidemiologic research?
A. Beneficence
B. Randomization
C. Stratification
D. Blinding
✔ A. Beneficence
RATIONALE: Beneficence requires maximizing benefits and minimizing harms in research.
