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Free Epidemiology and Biostatistics MCQs with Answers

50 Epidemiology and Biostatistics MCQs from Community Health Nursing, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Epidemiology examines the distribution and causes of disease by person, place and time, using measures such as incidence, prevalence, mortality and case-fatality rates. Biostatistics covers data presentation, sampling, averages, variability, probability and interpretation of study results, while distinguishing association from causation.

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50 questions · page 1 of 3

1. In epidemiology, which measure describes the number of new cases of a disease occurring in a population at risk during a specified period?

  • A. Point prevalence
  • B. Incidence
  • C. Case-fatality rate
  • D. Proportional mortality

Explanation: Incidence measures new cases that develop in a population at risk during a defined time.

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Correct answer: Incidence

2. A survey records all people currently living with hypertension in a district on 1 January. Which epidemiological measure is being estimated?

  • A. Point prevalence
  • B. Cumulative incidence
  • C. Attack rate
  • D. Case-fatality rate

Explanation: Point prevalence is the proportion of a population with a condition at one specific point in time.

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Correct answer: Point prevalence

3. In a district, 200 patients are diagnosed with typhoid fever and 10 of them die from the disease. Which measure is calculated as 10 divided by 200, multiplied by 100?

  • A. Crude mortality rate
  • B. Incidence rate
  • C. Case-fatality rate
  • D. Proportional morbidity rate

Explanation: The case-fatality rate is the percentage of diagnosed patients who die from the disease.

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Correct answer: Case-fatality rate

4. A Lady Health Worker selects every tenth household from an ordered list after choosing a random starting point. Which sampling method is used?

  • A. Convenience sampling
  • B. Systematic sampling
  • C. Purposive sampling
  • D. Cluster sampling

Explanation: Systematic sampling selects units at a fixed interval after a random start.

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Correct answer: Systematic sampling

5. The values of five patients' systolic blood pressure readings are 110, 120, 120, 130 and 150 mmHg. What is the median value?

  • A. 110 mmHg
  • B. 120 mmHg
  • C. 130 mmHg
  • D. 150 mmHg

Explanation: The median is the middle value when observations are arranged in order. The third value in this ordered set is 120 mmHg.

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Correct answer: 120 mmHg

6. A data set contains one extremely high value caused by a recording error. Which measure of central tendency is least affected by that extreme value?

  • A. Mean
  • B. Median
  • C. Arithmetic average
  • D. Weighted mean

Explanation: The median is based on the middle position and is less influenced by extreme observations.

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Correct answer: Median

7. A study reports that children who sleep fewer hours have more respiratory infections. Which finding would provide the strongest evidence that the association is not explained by a third variable?

  • A. The study has a large sample size
  • B. The association remains after controlling for age and household crowding
  • C. The participants come from one hospital
  • D. The infection diagnosis is based on symptoms alone

Explanation: Controlling for potential confounding variables, such as age and household crowding, helps determine whether the observed association…

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Correct answer: The association remains after controlling for age and household crowding

8. A screening test is used for tuberculosis in a group of people without symptoms. Which characteristic is most important when the aim is to identify nearly all people who may have the disease?

Hard
  • A. High sensitivity
  • B. High specificity
  • C. High positive predictive value
  • D. Low negative predictive value

Explanation: High sensitivity detects a large proportion of people who truly have the disease and produces few false-negative results.

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Correct answer: High sensitivity

9. During a dengue outbreak, a nurse records the number of cases by village, age group and week of onset. What is the main epidemiological purpose of this information?

  • A. To describe disease distribution by person, place and time
  • B. To prove that one treatment caused recovery
  • C. To calculate the average height of the population
  • D. To replace laboratory confirmation of every case

Explanation: Describing cases by person, place and time helps identify patterns, clusters and possible sources of infection.

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Correct answer: To describe disease distribution by person, place and time

10. A study finds that people who carry umbrellas are more likely to have wet clothing. Which conclusion is most appropriate?

Moderate
  • A. Umbrella use causes wet clothing
  • B. Wet clothing prevents umbrella use
  • C. The finding shows an association, not necessarily causation
  • D. The finding proves that rain has no effect

Explanation: The two factors are associated because both may be related to rainfall, which is a possible confounding factor.

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Correct answer: The finding shows an association, not necessarily causation

11. Which epidemiological measure expresses the number of deaths in a population during a specified period?

  • A. Mortality rate
  • B. Case-fatality rate
  • C. Attack rate
  • D. Survival rate

Explanation: Mortality rate relates deaths to the total population during a stated time.

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Correct answer: Mortality rate

12. During a food-poisoning outbreak, 40 of 200 people who ate at a wedding become ill. Which measure is represented by 40 divided by 200, multiplied by 100?

Hard
  • A. Attack rate
  • B. Mortality rate
  • C. Prevalence rate
  • D. Case-fatality rate

Explanation: An attack rate is the proportion of an exposed group that develops illness during an outbreak.

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Correct answer: Attack rate

13. The ages of four patients are 20, 30, 40 and 50 years. What is the arithmetic mean age?

  • A. 30 years
  • B. 35 years
  • C. 40 years
  • D. 45 years

Explanation: Add the ages and divide by the number of observations: 20 + 30 + 40 + 50 = 140, and 140 divided by 4 equals 35 years.

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Correct answer: 35 years

14. What does a large standard deviation indicate in a set of patient measurements?

  • A. Values are widely spread around the mean
  • B. Values are closely grouped around the mean
  • C. The sample contains no unusual values
  • D. The mean is equal to the median

Explanation: Standard deviation describes the spread of observations around the mean.

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Correct answer: Values are widely spread around the mean

15. A nurse wants to display the number of patients in different blood groups at a health centre. Which graph is most suitable?

  • A. Bar graph
  • B. Histogram
  • C. Scatter plot
  • D. Line graph

Explanation: Blood group is a categorical variable, so separate bars can compare the number in each category.

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Correct answer: Bar graph

16. A researcher in a rural health centre writes the names of all eligible households on slips, mixes them, and draws 30 slips. Which sampling method is being used?

  • A. Simple random sampling
  • B. Systematic sampling
  • C. Stratified sampling
  • D. Convenience sampling

Explanation: Each eligible household has an equal chance of selection when slips are mixed and drawn randomly.

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Correct answer: Simple random sampling

17. For a maternal health survey, a researcher divides women into urban and rural groups, then randomly selects participants from each group. Which sampling method is used?

Hard
  • A. Stratified random sampling
  • B. Cluster sampling
  • C. Purposive sampling
  • D. Snowball sampling

Explanation: Stratified sampling first divides the population into important subgroups and then samples from each subgroup.

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Correct answer: Stratified random sampling

18. A study reports a p-value of 0.02 for the difference in recovery time between two treatments. Assuming the significance level is 0.05, which interpretation is correct?

  • A. The difference is statistically significant
  • B. The treatments have identical effects
  • C. The study proves one treatment causes recovery
  • D. There is a 2% chance the data were collected

Explanation: Because 0.02 is less than 0.05, the result is statistically significant under the stated criterion.

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Correct answer: The difference is statistically significant

19. A study reports a relative risk of 1.8 for hepatitis infection among people with a particular exposure, with a 95% confidence interval of 1.2 to 2.7. What is the best interpretation?

  • A. The exposure is associated with higher risk
  • B. The exposure prevents hepatitis infection
  • C. The result proves the exposure causes infection
  • D. The exposure has exactly 1.8 times the risk in every person

Explanation: The relative risk above 1 indicates higher risk in the exposed group, and the interval does not include 1, supporting a statistically…

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Correct answer: The exposure is associated with higher risk

20. A cross-sectional survey finds that adults with poor housing are more likely to have tuberculosis. What is the main limitation when interpreting this finding?

  • A. Temporality cannot be established
  • B. The sample must contain only children
  • C. The result cannot show any association
  • D. The survey automatically proves causation

Explanation: Cross-sectional studies measure exposure and outcome at the same time, so they may not show which came first.

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Correct answer: Temporality cannot be established
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