Certified in Public Health (CPH®) Exam: 200 Practice
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1. The incidence rate of a disease is defined as:
A. The total number of existing cases at a specific point in time
B. The number of new cases in a population at risk over a specific time period
C. The proportion of deaths from a disease among those diagnosed
D. The number of cases per 100,000 population
Correct Answer: B. The number of new cases in a population at risk over a specific time period
Rationale: Incidence measures the occurrence of new cases in a population at risk over a
defined time period. Prevalence (A) is the total existing cases at a point in time. Case-fatality (C)
is deaths among cases. Incidence rate is typically expressed per 100,000 or 1,000 population.
2. A study that follows a group of individuals over time to observe the development of
disease is called a:
A. Cross-sectional study
B. Case-control study
C. Cohort study
D. Ecological study
Correct Answer: C. Cohort study
Rationale: A cohort study follows a group of individuals (cohort) over time to observe who
develops the disease. Case-control studies compare cases to controls retrospectively. Cross-
1
, sectional studies assess a population at a single point in time. Ecological studies use aggregate
data.
3. Which measure of association is used in a case-control study?
A. Relative risk
B. Odds ratio
C. Attributable risk
D. Incidence rate ratio
Correct Answer: B. Odds ratio
Rationale: The odds ratio is the measure of association used in case-control studies. Relative
risk is used in cohort studies. Attributable risk measures the excess risk in the exposed group.
4. A screening test has a sensitivity of 95% and a specificity of 90%. Sensitivity refers to:
A. The proportion of true negatives correctly identified
B. The proportion of true positives correctly identified
C. The proportion of positive tests that are true positives
D. The proportion of negative tests that are true negatives
Correct Answer: B. The proportion of true positives correctly identified
Rationale: Sensitivity is the ability of a test to correctly identify those with the disease (true
positives). Specificity (A) is the proportion of true negatives correctly identified. Predictive value
positive (C) is the proportion of positive tests that are true positives.
5. In a randomized controlled trial, the purpose of randomization is to:
A. Ensure equal numbers in each group
B. Eliminate bias in treatment assignment
C. Increase the sample size
D. Improve the generalizability of results
Correct Answer: B. Eliminate bias in treatment assignment
Rationale: Randomization ensures that each participant has an equal chance of being assigned
to treatment or control groups, reducing selection bias and balancing known and unknown
confounding factors.
2
, 6. The p-value in hypothesis testing represents:
A. The probability that the null hypothesis is true
B. The probability of observing the results if the null hypothesis is true
C. The probability that the alternative hypothesis is true
D. The magnitude of the effect
Correct Answer: B. The probability of observing the results if the null hypothesis is true
Rationale: The p-value is the probability of obtaining results as extreme as or more extreme
than those observed, assuming the null hypothesis is true. It does not represent the probability
that the null hypothesis is true.
7. A 95% confidence interval for a relative risk of 2.0 ranges from 1.2 to 3.5. This means:
A. There is a 95% chance that the true relative risk is between 1.2 and 3.5
B. We are 95% confident that the true relative risk falls between 1.2 and 3.5
C. The relative risk is statistically significant at the 0.05 level
D. Both B and C
Correct Answer: D. Both B and C
Rationale: A 95% confidence interval that does not include 1.0 indicates statistical significance
at the 0.05 level. The correct interpretation is that we are 95% confident that the true
parameter falls within the interval.
8. The epidemiological triad consists of:
A. Host, agent, and environment
B. Person, place, and time
C. Susceptibility, exposure, and outcome
D. Primary, secondary, and tertiary prevention
Correct Answer: A. Host, agent, and environment
Rationale: The epidemiological triad describes the interaction between host (susceptible
individual), agent (causative factor), and environment (external conditions) in disease causation.
Person, place, and time (B) are descriptive epidemiology categories.
3
, 9. Which study design provides the strongest evidence for causality?
A. Cross-sectional study
B. Case-control study
C. Randomized controlled trial
D. Ecological study
Correct Answer: C. Randomized controlled trial
Rationale: The randomized controlled trial (RCT) provides the strongest evidence for causality
because randomization minimizes bias and confounding. It is considered the gold standard for
evaluating interventions.
10. The number of deaths from a disease divided by the number of cases of that disease is
the:
A. Mortality rate
B. Case-fatality rate
C. Attack rate
D. Incidence rate
Correct Answer: B. Case-fatality rate
Rationale: Case-fatality rate is the proportion of cases that die from the disease. Mortality rate
(A) is deaths per population. Attack rate (C) is new cases per exposed population. Incidence rate
(D) is new cases per population at risk.
11. In a cross-sectional study, which of the following is true?
A. Exposure and outcome are measured at the same time
B. The study follows participants over time
C. The study is used to establish causality
D. The study is always prospective
Correct Answer: A. Exposure and outcome are measured at the same time
Rationale: Cross-sectional studies measure exposure and outcome simultaneously at a single
point in time. They are useful for estimating prevalence but cannot establish causality.
12. The standard deviation is a measure of:
4
Questions with Answers and Rationales Most Recent
Exam Actual Complete Real Exam Questions And Correct
Answers (Verified Answers) Already Graded A+ |
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1. The incidence rate of a disease is defined as:
A. The total number of existing cases at a specific point in time
B. The number of new cases in a population at risk over a specific time period
C. The proportion of deaths from a disease among those diagnosed
D. The number of cases per 100,000 population
Correct Answer: B. The number of new cases in a population at risk over a specific time period
Rationale: Incidence measures the occurrence of new cases in a population at risk over a
defined time period. Prevalence (A) is the total existing cases at a point in time. Case-fatality (C)
is deaths among cases. Incidence rate is typically expressed per 100,000 or 1,000 population.
2. A study that follows a group of individuals over time to observe the development of
disease is called a:
A. Cross-sectional study
B. Case-control study
C. Cohort study
D. Ecological study
Correct Answer: C. Cohort study
Rationale: A cohort study follows a group of individuals (cohort) over time to observe who
develops the disease. Case-control studies compare cases to controls retrospectively. Cross-
1
, sectional studies assess a population at a single point in time. Ecological studies use aggregate
data.
3. Which measure of association is used in a case-control study?
A. Relative risk
B. Odds ratio
C. Attributable risk
D. Incidence rate ratio
Correct Answer: B. Odds ratio
Rationale: The odds ratio is the measure of association used in case-control studies. Relative
risk is used in cohort studies. Attributable risk measures the excess risk in the exposed group.
4. A screening test has a sensitivity of 95% and a specificity of 90%. Sensitivity refers to:
A. The proportion of true negatives correctly identified
B. The proportion of true positives correctly identified
C. The proportion of positive tests that are true positives
D. The proportion of negative tests that are true negatives
Correct Answer: B. The proportion of true positives correctly identified
Rationale: Sensitivity is the ability of a test to correctly identify those with the disease (true
positives). Specificity (A) is the proportion of true negatives correctly identified. Predictive value
positive (C) is the proportion of positive tests that are true positives.
5. In a randomized controlled trial, the purpose of randomization is to:
A. Ensure equal numbers in each group
B. Eliminate bias in treatment assignment
C. Increase the sample size
D. Improve the generalizability of results
Correct Answer: B. Eliminate bias in treatment assignment
Rationale: Randomization ensures that each participant has an equal chance of being assigned
to treatment or control groups, reducing selection bias and balancing known and unknown
confounding factors.
2
, 6. The p-value in hypothesis testing represents:
A. The probability that the null hypothesis is true
B. The probability of observing the results if the null hypothesis is true
C. The probability that the alternative hypothesis is true
D. The magnitude of the effect
Correct Answer: B. The probability of observing the results if the null hypothesis is true
Rationale: The p-value is the probability of obtaining results as extreme as or more extreme
than those observed, assuming the null hypothesis is true. It does not represent the probability
that the null hypothesis is true.
7. A 95% confidence interval for a relative risk of 2.0 ranges from 1.2 to 3.5. This means:
A. There is a 95% chance that the true relative risk is between 1.2 and 3.5
B. We are 95% confident that the true relative risk falls between 1.2 and 3.5
C. The relative risk is statistically significant at the 0.05 level
D. Both B and C
Correct Answer: D. Both B and C
Rationale: A 95% confidence interval that does not include 1.0 indicates statistical significance
at the 0.05 level. The correct interpretation is that we are 95% confident that the true
parameter falls within the interval.
8. The epidemiological triad consists of:
A. Host, agent, and environment
B. Person, place, and time
C. Susceptibility, exposure, and outcome
D. Primary, secondary, and tertiary prevention
Correct Answer: A. Host, agent, and environment
Rationale: The epidemiological triad describes the interaction between host (susceptible
individual), agent (causative factor), and environment (external conditions) in disease causation.
Person, place, and time (B) are descriptive epidemiology categories.
3
, 9. Which study design provides the strongest evidence for causality?
A. Cross-sectional study
B. Case-control study
C. Randomized controlled trial
D. Ecological study
Correct Answer: C. Randomized controlled trial
Rationale: The randomized controlled trial (RCT) provides the strongest evidence for causality
because randomization minimizes bias and confounding. It is considered the gold standard for
evaluating interventions.
10. The number of deaths from a disease divided by the number of cases of that disease is
the:
A. Mortality rate
B. Case-fatality rate
C. Attack rate
D. Incidence rate
Correct Answer: B. Case-fatality rate
Rationale: Case-fatality rate is the proportion of cases that die from the disease. Mortality rate
(A) is deaths per population. Attack rate (C) is new cases per exposed population. Incidence rate
(D) is new cases per population at risk.
11. In a cross-sectional study, which of the following is true?
A. Exposure and outcome are measured at the same time
B. The study follows participants over time
C. The study is used to establish causality
D. The study is always prospective
Correct Answer: A. Exposure and outcome are measured at the same time
Rationale: Cross-sectional studies measure exposure and outcome simultaneously at a single
point in time. They are useful for estimating prevalence but cannot establish causality.
12. The standard deviation is a measure of:
4
