Biostatistics RxPrep Naplex Guide
1. Which type of data is characterized by an absolute zero and meaningful ratios?
A. Nominal
B. Ordinal
C. Interval
D. Ratio
Correct Answer: D
Rationale: Ratio data has a true zero point, allowing for meaningful ratio comparisons.
Heart rate, weight, and blood pressure are examples where zero means the complete absence
of the variable . Interval data (e.g., temperature in Celsius) lacks a meaningful zero, while
nominal and ordinal data are categorical .
2. A researcher collects pain scores using a 0–10 numeric rating scale. This is best classified as:
A. Nominal data
B. Ordinal data
C. Interval data
D. Ratio data
Correct Answer: B
Rationale: Ordinal data consists of ranked categories where the difference between ranks is
not equal. A pain score of 8 versus 6 does not represent the same magnitude of difference as 4
versus 2 . Nominal data has no order, interval data has equal intervals but no true zero, and ratio
data has an absolute zero.
3. In a study examining the relationship between a rare disease and prior exposure, which study
design is most appropriate?
A. Randomized controlled trial
B. Prospective cohort study
C. Case-control study
D. Cross-sectional study
Correct Answer: C
Rationale: Case-control studies are efficient for rare outcomes because they start with the
outcome (cases) and look back for exposures. They yield odds ratios rather than relative risks .
,Randomized controlled trials are unethical or impractical for rare diseases, and cohort studies
would require very large sample sizes.
4. Which measure of central tendency is most appropriate for nominal data?
A. Mean
B. Median
C. Mode
D. Standard deviation
Correct Answer: C
Rationale: The mode is the only measure of central tendency appropriate for nominal data
because it identifies the most frequent category without requiring numerical ordering . Mean
requires interval or ratio data, and median requires ordinal or higher data.
5. A clinical trial randomly assigns patients to either a new drug or placebo and follows them
prospectively for cardiovascular events. This is a:
A. Case-control study
B. Cohort study
C. Randomized controlled trial
D. Cross-sectional study
Correct Answer: C
Rationale: A randomized controlled trial is characterized by random assignment to
intervention groups and prospective follow-up for outcomes . This design minimizes
confounding and allows calculation of relative risk and absolute risk reduction.
6. Which of the following is an example of discrete data?
A. Serum creatinine
B. Number of hospitalizations
C. Body temperature
D. Blood pressure
Correct Answer: B
Rationale: Discrete data can only take specific values, typically whole numbers. The number
of hospitalizations is counted, not measured on a continuous scale . Serum creatinine,
temperature, and blood pressure are continuous variables.
,7. A study reports that patients with a specific genetic polymorphism have 3.2 times the odds of
developing a drug-induced liver injury compared to those without the polymorphism. What
type of measure is this?
A. Relative risk
B. Absolute risk reduction
C. Odds ratio
D. Hazard ratio
Correct Answer: C
Rationale: The odds ratio compares the odds of an outcome in an exposed group versus an
unexposed group. It is the standard measure in case-control studies and is often reported in
pharmacogenomic studies .
8. Which study design is most susceptible to recall bias?
A. Prospective cohort study
B. Randomized controlled trial
C. Case-control study
D. Cross-sectional study
Correct Answer: C
Rationale: Case-control studies require participants to recall past exposures, which can be
influenced by their current disease status (recall bias). Prospective designs collect exposure data
before outcomes occur, minimizing this bias .
9. In a 2x2 contingency table, which cells are used to calculate the odds ratio in a case-control
study?
A. (Cases exposed × Controls unexposed) / (Cases unexposed × Controls exposed)
B. (Cases exposed × Cases unexposed) / (Controls exposed × Controls unexposed)
C. (Total cases × Total controls) / (Total exposed × Total unexposed)
D. (Cases exposed × Controls exposed) / (Cases unexposed × Controls unexposed)
Correct Answer: A
Rationale: The odds ratio in a case-control study is calculated as (a × d) / (b × c), where a =
cases exposed, b = cases unexposed, c = controls exposed, d = controls unexposed. This formula
yields the cross-product ratio .
10. Which of the following statements about the null hypothesis is correct?
, A. It states that there is a significant difference between groups
B. It is what researchers aim to prove
C. It states that there is no significant difference between groups
D. It is always rejected in clinical trials
Correct Answer: C
Rationale: The null hypothesis (H₀) states that there is no difference or association between
variables. Researchers attempt to reject the null hypothesis in favor of the alternative
hypothesis, which proposes a significant difference exists .
11. A researcher wants to compare mean blood pressure reductions across three different
antihypertensive medications. Which statistical test is most appropriate?
A. Paired t-test
B. Student's t-test
C. Analysis of variance (ANOVA)
D. Chi-square test
Correct Answer: C
Rationale: ANOVA is used when comparing means across three or more groups. T-tests are
limited to comparing two groups. The chi-square test is used for categorical data comparisons .
12. In a cohort study, 15% of smokers and 5% of non-smokers develop a specific disease. What
is the relative risk?
A. 0.33
B. 1.5
C. 3.0
D. 10.0
Correct Answer: C
Rationale: Relative risk = risk in exposed / risk in unexposed = 0..05 = 3.0. This means
smokers have three times the risk of developing the disease compared to non-smokers .
13. Which measure of disease frequency incorporates a time dimension and is most appropriate
for dynamic populations?
A. Prevalence
B. Incidence rate
C. Point prevalence
D. Cumulative incidence
1. Which type of data is characterized by an absolute zero and meaningful ratios?
A. Nominal
B. Ordinal
C. Interval
D. Ratio
Correct Answer: D
Rationale: Ratio data has a true zero point, allowing for meaningful ratio comparisons.
Heart rate, weight, and blood pressure are examples where zero means the complete absence
of the variable . Interval data (e.g., temperature in Celsius) lacks a meaningful zero, while
nominal and ordinal data are categorical .
2. A researcher collects pain scores using a 0–10 numeric rating scale. This is best classified as:
A. Nominal data
B. Ordinal data
C. Interval data
D. Ratio data
Correct Answer: B
Rationale: Ordinal data consists of ranked categories where the difference between ranks is
not equal. A pain score of 8 versus 6 does not represent the same magnitude of difference as 4
versus 2 . Nominal data has no order, interval data has equal intervals but no true zero, and ratio
data has an absolute zero.
3. In a study examining the relationship between a rare disease and prior exposure, which study
design is most appropriate?
A. Randomized controlled trial
B. Prospective cohort study
C. Case-control study
D. Cross-sectional study
Correct Answer: C
Rationale: Case-control studies are efficient for rare outcomes because they start with the
outcome (cases) and look back for exposures. They yield odds ratios rather than relative risks .
,Randomized controlled trials are unethical or impractical for rare diseases, and cohort studies
would require very large sample sizes.
4. Which measure of central tendency is most appropriate for nominal data?
A. Mean
B. Median
C. Mode
D. Standard deviation
Correct Answer: C
Rationale: The mode is the only measure of central tendency appropriate for nominal data
because it identifies the most frequent category without requiring numerical ordering . Mean
requires interval or ratio data, and median requires ordinal or higher data.
5. A clinical trial randomly assigns patients to either a new drug or placebo and follows them
prospectively for cardiovascular events. This is a:
A. Case-control study
B. Cohort study
C. Randomized controlled trial
D. Cross-sectional study
Correct Answer: C
Rationale: A randomized controlled trial is characterized by random assignment to
intervention groups and prospective follow-up for outcomes . This design minimizes
confounding and allows calculation of relative risk and absolute risk reduction.
6. Which of the following is an example of discrete data?
A. Serum creatinine
B. Number of hospitalizations
C. Body temperature
D. Blood pressure
Correct Answer: B
Rationale: Discrete data can only take specific values, typically whole numbers. The number
of hospitalizations is counted, not measured on a continuous scale . Serum creatinine,
temperature, and blood pressure are continuous variables.
,7. A study reports that patients with a specific genetic polymorphism have 3.2 times the odds of
developing a drug-induced liver injury compared to those without the polymorphism. What
type of measure is this?
A. Relative risk
B. Absolute risk reduction
C. Odds ratio
D. Hazard ratio
Correct Answer: C
Rationale: The odds ratio compares the odds of an outcome in an exposed group versus an
unexposed group. It is the standard measure in case-control studies and is often reported in
pharmacogenomic studies .
8. Which study design is most susceptible to recall bias?
A. Prospective cohort study
B. Randomized controlled trial
C. Case-control study
D. Cross-sectional study
Correct Answer: C
Rationale: Case-control studies require participants to recall past exposures, which can be
influenced by their current disease status (recall bias). Prospective designs collect exposure data
before outcomes occur, minimizing this bias .
9. In a 2x2 contingency table, which cells are used to calculate the odds ratio in a case-control
study?
A. (Cases exposed × Controls unexposed) / (Cases unexposed × Controls exposed)
B. (Cases exposed × Cases unexposed) / (Controls exposed × Controls unexposed)
C. (Total cases × Total controls) / (Total exposed × Total unexposed)
D. (Cases exposed × Controls exposed) / (Cases unexposed × Controls unexposed)
Correct Answer: A
Rationale: The odds ratio in a case-control study is calculated as (a × d) / (b × c), where a =
cases exposed, b = cases unexposed, c = controls exposed, d = controls unexposed. This formula
yields the cross-product ratio .
10. Which of the following statements about the null hypothesis is correct?
, A. It states that there is a significant difference between groups
B. It is what researchers aim to prove
C. It states that there is no significant difference between groups
D. It is always rejected in clinical trials
Correct Answer: C
Rationale: The null hypothesis (H₀) states that there is no difference or association between
variables. Researchers attempt to reject the null hypothesis in favor of the alternative
hypothesis, which proposes a significant difference exists .
11. A researcher wants to compare mean blood pressure reductions across three different
antihypertensive medications. Which statistical test is most appropriate?
A. Paired t-test
B. Student's t-test
C. Analysis of variance (ANOVA)
D. Chi-square test
Correct Answer: C
Rationale: ANOVA is used when comparing means across three or more groups. T-tests are
limited to comparing two groups. The chi-square test is used for categorical data comparisons .
12. In a cohort study, 15% of smokers and 5% of non-smokers develop a specific disease. What
is the relative risk?
A. 0.33
B. 1.5
C. 3.0
D. 10.0
Correct Answer: C
Rationale: Relative risk = risk in exposed / risk in unexposed = 0..05 = 3.0. This means
smokers have three times the risk of developing the disease compared to non-smokers .
13. Which measure of disease frequency incorporates a time dimension and is most appropriate
for dynamic populations?
A. Prevalence
B. Incidence rate
C. Point prevalence
D. Cumulative incidence
