Epidemiology & Biostatistics Exam 2026
Edition Questions ,Answers & Detailed
Rationales
1. A researcher wants to determine the prevalence of
hypertension among adults in a city by measuring blood
pressure in a randomly selected sample at one point in time.
Which study design is most appropriate?
A. Cohort study
B. Case-control study
C. Cross-sectional study
D. Randomized controlled trial
Answer: C. Cross-sectional study
Rationale: A cross-sectional study assesses exposure and
disease status at a single point in time and is commonly used to
estimate disease prevalence.
2. Investigators follow 5,000 individuals who smoke and 5,000
individuals who do not smoke for 20 years to compare the
,incidence of lung cancer. Which measure is most directly
calculated from this study?
A. Odds ratio
B. Relative risk
C. Prevalence ratio
D. Case-fatality rate
Answer: B. Relative risk
Rationale: A cohort study allows direct calculation of disease
incidence in exposed and unexposed groups, making relative
risk an appropriate measure of association.
3. A study identifies patients with pancreatic cancer and a
group of individuals without pancreatic cancer and compares
their previous exposure to cigarette smoking. Which measure
of association is most appropriate?
A. Relative risk
B. Odds ratio
C. Risk difference
D. Incidence rate
Answer: B. Odds ratio
,Rationale: Case-control studies begin with disease status and
retrospectively assess exposure. The odds ratio is the standard
measure of association.
4. A new screening test is evaluated in 1,000 people. Of 100
individuals who truly have disease, 90 test positive. What is the
sensitivity of the test?
A. 9%
B. 10%
C. 90%
D. 99%
Answer: C. 90%
Rationale: Sensitivity = true positives ÷ all individuals with
disease. Therefore, 90 ÷ 100 = 90%.
5. A diagnostic test has a specificity of 95%. Which statement
best describes this characteristic?
A. It correctly identifies 95% of people with disease
B. It correctly identifies 95% of people without disease
C. It has a 95% positive predictive value
D. It has a 5% false-negative rate
, Answer: B. It correctly identifies 95% of people without
disease
Rationale: Specificity is the proportion of individuals without
disease who test negative. A highly specific test has a low false-
positive rate.
6. A disease has a prevalence of 1% in a population. A highly
sensitive screening test is used. Which factor is most likely to
reduce the positive predictive value of the test?
A. High disease prevalence
B. Low disease prevalence
C. High specificity
D. Large sample size
Answer: B. Low disease prevalence
Rationale: Positive predictive value decreases when disease
prevalence is low because false-positive results may
substantially outnumber true-positive results.
7. A researcher wants to minimize selection bias when selecting
participants for a study. Which method is most appropriate?
A. Convenience sampling
B. Snowball sampling
Edition Questions ,Answers & Detailed
Rationales
1. A researcher wants to determine the prevalence of
hypertension among adults in a city by measuring blood
pressure in a randomly selected sample at one point in time.
Which study design is most appropriate?
A. Cohort study
B. Case-control study
C. Cross-sectional study
D. Randomized controlled trial
Answer: C. Cross-sectional study
Rationale: A cross-sectional study assesses exposure and
disease status at a single point in time and is commonly used to
estimate disease prevalence.
2. Investigators follow 5,000 individuals who smoke and 5,000
individuals who do not smoke for 20 years to compare the
,incidence of lung cancer. Which measure is most directly
calculated from this study?
A. Odds ratio
B. Relative risk
C. Prevalence ratio
D. Case-fatality rate
Answer: B. Relative risk
Rationale: A cohort study allows direct calculation of disease
incidence in exposed and unexposed groups, making relative
risk an appropriate measure of association.
3. A study identifies patients with pancreatic cancer and a
group of individuals without pancreatic cancer and compares
their previous exposure to cigarette smoking. Which measure
of association is most appropriate?
A. Relative risk
B. Odds ratio
C. Risk difference
D. Incidence rate
Answer: B. Odds ratio
,Rationale: Case-control studies begin with disease status and
retrospectively assess exposure. The odds ratio is the standard
measure of association.
4. A new screening test is evaluated in 1,000 people. Of 100
individuals who truly have disease, 90 test positive. What is the
sensitivity of the test?
A. 9%
B. 10%
C. 90%
D. 99%
Answer: C. 90%
Rationale: Sensitivity = true positives ÷ all individuals with
disease. Therefore, 90 ÷ 100 = 90%.
5. A diagnostic test has a specificity of 95%. Which statement
best describes this characteristic?
A. It correctly identifies 95% of people with disease
B. It correctly identifies 95% of people without disease
C. It has a 95% positive predictive value
D. It has a 5% false-negative rate
, Answer: B. It correctly identifies 95% of people without
disease
Rationale: Specificity is the proportion of individuals without
disease who test negative. A highly specific test has a low false-
positive rate.
6. A disease has a prevalence of 1% in a population. A highly
sensitive screening test is used. Which factor is most likely to
reduce the positive predictive value of the test?
A. High disease prevalence
B. Low disease prevalence
C. High specificity
D. Large sample size
Answer: B. Low disease prevalence
Rationale: Positive predictive value decreases when disease
prevalence is low because false-positive results may
substantially outnumber true-positive results.
7. A researcher wants to minimize selection bias when selecting
participants for a study. Which method is most appropriate?
A. Convenience sampling
B. Snowball sampling
