BIOSTATISTICS FINAL EXAM PRACTICE QUESTIONS
AND 100% VERIFIED ANSWERS PLUS RATIONALES 2026.
1. Which measure of central tendency is most affected by extreme values?
A. Mean
B. Median
C. Mode
D. Range
Correct Answer: A
Rationale: The mean is highly sensitive to outliers, whereas the median and mode are
more robust. Range is not a measure of central tendency.
2. A dataset has a mean of 50 and a standard deviation of 10. What is the z-score for a
value of 70?
A. 1
B. 2
C. 3
D. -2
Correct Answer: B
Rationale: z = (X - mean)/SD = (70 - 50)/10 = 2. Other options are incorrect
calculations.
3. Which study design is best suited to determine causality?
A. Cross-sectional study
B. Case-control study
C. Randomized controlled trial
D. Ecological study
Correct Answer: C
Rationale: Randomized controlled trials minimize bias and allow causal inference.
Other designs are observational.
4. What is the main purpose of randomization in clinical trials?
A. Increase sample size
B. Reduce bias
C. Improve measurement accuracy
D. Eliminate confounding variables completely
Correct Answer: B
Rationale: Randomization reduces selection bias and balances confounders, though it
does not eliminate them entirely.
,5. Which of the following is a non-parametric test?
A. t-test
B. ANOVA
C. Chi-square test
D. Pearson correlation
Correct Answer: C
Rationale: Chi-square does not assume normal distribution. Others are parametric
tests.
6. In hypothesis testing, a Type I error occurs when:
A. Accepting a false null hypothesis
B. Rejecting a true null hypothesis
C. Rejecting a false null hypothesis
D. Accepting a true null hypothesis
Correct Answer: B
Rationale: Type I error is a false positive—rejecting a true null hypothesis.
7. The p-value represents:
A. Probability that the null hypothesis is true
B. Probability of observing data given the null hypothesis
C. Probability of Type II error
D. Confidence level
Correct Answer: B
Rationale: The p-value is the probability of observed results assuming the null
hypothesis is true.
8. Which measure describes the spread of data around the mean?
A. Median
B. Variance
C. Mode
D. Percentile
Correct Answer: B
Rationale: Variance quantifies dispersion around the mean. Median and mode
measure central tendency.
9. A confidence interval provides:
A. Exact population parameter
B. Range likely containing the parameter
C. Probability of hypothesis being true
D. Sample mean only
Correct Answer: B
, Rationale: Confidence intervals estimate a range where the population parameter
likely lies.
10. Which sampling method gives every individual an equal chance of selection?
A. Stratified sampling
B. Cluster sampling
C. Simple random sampling
D. Convenience sampling
Correct Answer: C
Rationale: Simple random sampling ensures equal probability for all individuals.
11. The null hypothesis typically states:
A. There is a difference
B. There is an association
C. There is no effect or difference
D. Data is skewed
Correct Answer: C
Rationale: The null hypothesis assumes no difference or association.
12. Which test compares means of more than two groups?
A. t-test
B. ANOVA
C. Chi-square
D. Regression
Correct Answer: B
Rationale: ANOVA is used to compare means across multiple groups.
13. Sensitivity of a test refers to:
A. True negative rate
B. True positive rate
C. False positive rate
D. Predictive value
Correct Answer: B
Rationale: Sensitivity measures the ability to correctly identify diseased individuals.
14. Specificity refers to:
A. True positive rate
B. True negative rate
C. False negative rate
D. Prevalence
, Correct Answer: B
Rationale: Specificity measures correctly identifying non-diseased individuals.
15. Which correlation coefficient indicates strongest relationship?
A. 0.2
B. -0.3
C. 0.9
D. 0
Correct Answer: C
Rationale: Values closer to ±1 indicate stronger relationships; 0.9 is strongest here.
16. A skewed distribution means:
A. Symmetrical data
B. Data with equal mean and median
C. Asymmetrical data
D. Uniform distribution
Correct Answer: C
Rationale: Skewness indicates asymmetry in distribution.
17. Which graph is best for categorical data?
A. Histogram
B. Bar chart
C. Scatter plot
D. Line graph
Correct Answer: B
Rationale: Bar charts are ideal for categorical data representation.
18. Incidence rate measures:
A. Total cases
B. New cases over time
C. Death rate
D. Recovery rate
Correct Answer: B
Rationale: Incidence refers to new cases in a population over time.
19. Prevalence measures:
A. New cases only
B. Existing cases at a point
C. Mortality
D. Risk ratio
AND 100% VERIFIED ANSWERS PLUS RATIONALES 2026.
1. Which measure of central tendency is most affected by extreme values?
A. Mean
B. Median
C. Mode
D. Range
Correct Answer: A
Rationale: The mean is highly sensitive to outliers, whereas the median and mode are
more robust. Range is not a measure of central tendency.
2. A dataset has a mean of 50 and a standard deviation of 10. What is the z-score for a
value of 70?
A. 1
B. 2
C. 3
D. -2
Correct Answer: B
Rationale: z = (X - mean)/SD = (70 - 50)/10 = 2. Other options are incorrect
calculations.
3. Which study design is best suited to determine causality?
A. Cross-sectional study
B. Case-control study
C. Randomized controlled trial
D. Ecological study
Correct Answer: C
Rationale: Randomized controlled trials minimize bias and allow causal inference.
Other designs are observational.
4. What is the main purpose of randomization in clinical trials?
A. Increase sample size
B. Reduce bias
C. Improve measurement accuracy
D. Eliminate confounding variables completely
Correct Answer: B
Rationale: Randomization reduces selection bias and balances confounders, though it
does not eliminate them entirely.
,5. Which of the following is a non-parametric test?
A. t-test
B. ANOVA
C. Chi-square test
D. Pearson correlation
Correct Answer: C
Rationale: Chi-square does not assume normal distribution. Others are parametric
tests.
6. In hypothesis testing, a Type I error occurs when:
A. Accepting a false null hypothesis
B. Rejecting a true null hypothesis
C. Rejecting a false null hypothesis
D. Accepting a true null hypothesis
Correct Answer: B
Rationale: Type I error is a false positive—rejecting a true null hypothesis.
7. The p-value represents:
A. Probability that the null hypothesis is true
B. Probability of observing data given the null hypothesis
C. Probability of Type II error
D. Confidence level
Correct Answer: B
Rationale: The p-value is the probability of observed results assuming the null
hypothesis is true.
8. Which measure describes the spread of data around the mean?
A. Median
B. Variance
C. Mode
D. Percentile
Correct Answer: B
Rationale: Variance quantifies dispersion around the mean. Median and mode
measure central tendency.
9. A confidence interval provides:
A. Exact population parameter
B. Range likely containing the parameter
C. Probability of hypothesis being true
D. Sample mean only
Correct Answer: B
, Rationale: Confidence intervals estimate a range where the population parameter
likely lies.
10. Which sampling method gives every individual an equal chance of selection?
A. Stratified sampling
B. Cluster sampling
C. Simple random sampling
D. Convenience sampling
Correct Answer: C
Rationale: Simple random sampling ensures equal probability for all individuals.
11. The null hypothesis typically states:
A. There is a difference
B. There is an association
C. There is no effect or difference
D. Data is skewed
Correct Answer: C
Rationale: The null hypothesis assumes no difference or association.
12. Which test compares means of more than two groups?
A. t-test
B. ANOVA
C. Chi-square
D. Regression
Correct Answer: B
Rationale: ANOVA is used to compare means across multiple groups.
13. Sensitivity of a test refers to:
A. True negative rate
B. True positive rate
C. False positive rate
D. Predictive value
Correct Answer: B
Rationale: Sensitivity measures the ability to correctly identify diseased individuals.
14. Specificity refers to:
A. True positive rate
B. True negative rate
C. False negative rate
D. Prevalence
, Correct Answer: B
Rationale: Specificity measures correctly identifying non-diseased individuals.
15. Which correlation coefficient indicates strongest relationship?
A. 0.2
B. -0.3
C. 0.9
D. 0
Correct Answer: C
Rationale: Values closer to ±1 indicate stronger relationships; 0.9 is strongest here.
16. A skewed distribution means:
A. Symmetrical data
B. Data with equal mean and median
C. Asymmetrical data
D. Uniform distribution
Correct Answer: C
Rationale: Skewness indicates asymmetry in distribution.
17. Which graph is best for categorical data?
A. Histogram
B. Bar chart
C. Scatter plot
D. Line graph
Correct Answer: B
Rationale: Bar charts are ideal for categorical data representation.
18. Incidence rate measures:
A. Total cases
B. New cases over time
C. Death rate
D. Recovery rate
Correct Answer: B
Rationale: Incidence refers to new cases in a population over time.
19. Prevalence measures:
A. New cases only
B. Existing cases at a point
C. Mortality
D. Risk ratio
