20 Epidemiology Quiz Questions and Answers

1. Question: What is the primary measure of disease frequency that indicates the number of new cases occurring in a population over a specific time period?
A) Prevalence
B) Incidence
C) Mortality rate
D) Case fatality rate
Answer: B
Explanation: Incidence specifically measures the rate of new occurrences of a disease in a population at risk during a defined period, which is crucial for assessing disease risk and trends.

2. Question: In a cohort study, participants are selected based on:
A) Their disease status
B) Their exposure status
C) Random allocation to treatment
D) The presence of confounding variables
Answer: B
Explanation: Cohort studies select participants based on exposure status and follow them over time to observe outcomes, allowing for the establishment of temporality between exposure and disease.

3. Question: Which type of bias occurs when the way data is collected differs between exposed and unexposed groups?
A) Selection bias
B) Information bias
C) Confounding bias
D) Recall bias
Answer: B
Explanation: Information bias arises from inaccuracies in data collection that vary between groups, potentially distorting the association between exposure and outcome.

4. Question: What does the relative risk (RR) represent in epidemiological studies?
A) The total number of cases in a population
B) The ratio of incidence rates in exposed vs. unexposed groups
C) The difference in prevalence between two populations
D) The probability of disease survival
Answer: B
Explanation: Relative risk compares the incidence of disease in exposed individuals to that in unexposed individuals, quantifying the strength of association.

5. Question: In an outbreak investigation, the first step is typically:
A) Implementing control measures
B) Verifying the diagnosis
C) Conducting a case-control study
D) Calculating attack rates
Answer: B
Explanation: Verifying the diagnosis ensures that the reported cases are accurate, preventing misdirection of resources and efforts in the investigation.

6. Question: What is the definition of endemic disease?
A) A disease that occurs sporadically and unpredictably
B) A disease constantly present in a population at a low level
C) A disease that spreads rapidly across continents
D) A disease that has been eradicated globally
Answer: B
Explanation: Endemic refers to the constant presence of a disease within a geographic area or population at a baseline level, as opposed to epidemic or pandemic levels.

7. Question: Which epidemiological study design is most efficient for rare diseases?
A) Cross-sectional study
B) Cohort study
C) Case-control study
D) Randomized controlled trial
Answer: C
Explanation: Case-control studies are efficient for rare diseases because they start with cases and controls and work backwards to identify exposures, requiring fewer participants.

8. Question: What is confounding in epidemiology?
A) A bias in data collection
B) A factor that distorts the true association between exposure and outcome
C) Random error in measurements
D) The direct cause of a disease
Answer: B
Explanation: Confounding occurs when an extraneous factor is associated with both the exposure and the outcome, leading to a false estimate of the exposure-outcome relationship.

9. Question: The attributable risk represents:
A) The total risk of disease in a population
B) The proportion of disease risk in exposed individuals that can be attributed to the exposure
C) The absolute difference in risk between exposed and unexposed groups
D) The rate of disease transmission
Answer: C
Explanation: Attributable risk measures the absolute difference in disease incidence between exposed and unexposed groups, indicating the excess risk due to the exposure.

10. Question: In screening programs, sensitivity is defined as:
A) The probability that a test correctly identifies those without the disease
B) The probability that a test correctly identifies those with the disease
C) The overall accuracy of the test
D) The false positive rate
Answer: B
Explanation: Sensitivity measures the test’s ability to correctly identify true positives, which is essential for ensuring that individuals with the disease are not missed.

11. Question: What is the basic reproduction number (R0) in infectious disease epidemiology?
A) The total number of cases in an outbreak
B) The average number of secondary cases produced by one infected individual in a susceptible population
C) The rate of disease recovery
D) The prevalence of immunity in a population
Answer: B
Explanation: R0 quantifies the transmissibility of an infectious agent, helping to predict whether an epidemic will occur (R0 > 1 indicates potential spread).

12. Question: Which measure is used to assess the proportion of a population affected by a disease at a given time?
A) Incidence rate
B) Prevalence rate
C) Mortality rate
D) Incidence proportion
Answer: B
Explanation: Prevalence rate indicates the proportion of individuals in a population who have the disease at a specific point or period, reflecting the disease burden.

13. Question: In a randomized controlled trial, the purpose of randomization is to:
A) Ensure equal distribution of confounding factors
B) Select only exposed individuals
C) Minimize information bias
D) Increase the sample size
Answer: A
Explanation: Randomization helps to evenly distribute both known and unknown confounders between groups, reducing bias and improving the validity of results.

14. Question: What does a p-value less than 0.05 indicate in epidemiological analysis?
A) The results are practically significant
B) The observed association is unlikely due to chance alone
C) The study has no bias
D) The exposure causes the outcome
Answer: B
Explanation: A p-value < 0.05 suggests that the probability of obtaining the observed results by random chance is less than 5%, supporting statistical significance. 15. Question: Herd immunity occurs when: A) All individuals in a population are vaccinated B) A sufficient proportion of the population is immune, reducing disease transmission C) A disease is eradicated globally D) Only exposed individuals are protected Answer: B Explanation: Herd immunity protects unvaccinated individuals by lowering the overall transmission rate when a large portion of the population is immune. 16. Question: Which of the following is an example of a point source epidemic? A) A seasonal flu outbreak in a community B) Food poisoning from a contaminated event meal C) A pandemic spread over years D) An endemic disease in a region Answer: B Explanation: A point source epidemic results from exposure to a common source at a single point in time, like contaminated food, leading to cases appearing simultaneously. 17. Question: The odds ratio is commonly used in which study design? A) Cohort studies B) Cross-sectional studies C) Case-control studies D) Randomized trials Answer: C Explanation: Odds ratio estimates the strength of association between exposure and outcome in case-control studies, where incidence rates are not directly measurable. 18. Question: What is the key limitation of cross-sectional studies? A) They cannot establish temporality B) They are expensive to conduct C) They require large samples D) They eliminate bias Answer: A Explanation: Cross-sectional studies collect data at a single point, making it difficult to determine whether exposure preceded the outcome, thus limiting causal inference. 19. Question: In epidemiology, the incubation period is: A) The time from exposure to symptom onset B) The duration of the disease C) The period after recovery D) The time for disease transmission Answer: A Explanation: The incubation period is the interval between exposure to a pathogen and the appearance of symptoms, which is vital for tracking and controlling outbreaks. 20. Question: What is the purpose of adjusting for confounders in epidemiological analysis? A) To increase the sample size B) To minimize the effect of extraneous variables on the exposure-outcome relationship C) To introduce bias D) To calculate prevalence Answer: B Explanation: Adjusting for confounders helps to isolate the true effect of the exposure on the outcome by controlling for variables that could distort the association.