BHS Research Methods and Biostatistics 1 — Questions and Answers
Question 1: In a randomized controlled trial (RCT), what is the primary purpose of randomization?
- To equally distribute known and unknown confounding variables between study groups (Correct answer)
- To ensure all participants volunteer willingly
- To make the study easier to blind
- To reduce the cost of data collection
Correct answer: To equally distribute known and unknown confounding variables between study groups
Randomization distributes both known and unknown confounders evenly across treatment and control groups, allowing causal inferences about the intervention's effect.
Question 2: Which type of epidemiological study design follows a group of people over time to see who develops a disease?
- Cohort study (Correct answer)
- Case-control study
- Cross-sectional study
- Ecological study
Correct answer: Cohort study
A cohort study follows a defined group (cohort) prospectively over time, comparing disease incidence between exposed and unexposed individuals.
Question 3: In statistics, what does a p-value of 0.05 conventionally indicate?
- There is a 5% probability that the observed results occurred by chance if the null hypothesis is true (Correct answer)
- The study has a 95% chance of detecting a true effect
- The effect size is clinically significant
- The results apply to 95% of the population
Correct answer: There is a 5% probability that the observed results occurred by chance if the null hypothesis is true
A p-value of 0.05 means there is a 5% probability of observing the data (or more extreme) if there is truly no effect, which is the conventional threshold for statistical significance.
Question 4: What is 'informed consent' in health research, and which historical event made it a cornerstone of research ethics?
- Voluntary agreement after disclosure of risks/benefits; the Nuremberg Trials exposed unethical Nazi experiments (Correct answer)
- Mandatory participation for public health benefit; the Tuskegee Study established this
- Institutional approval for data collection; established by the Declaration of Helsinki
- Patient rights to refuse treatment; established by the Patient Bill of Rights
Correct answer: Voluntary agreement after disclosure of risks/benefits; the Nuremberg Trials exposed unethical Nazi experiments
Informed consent requires that research participants voluntarily agree after being fully informed of risks and benefits; the Nuremberg Code emerged from post-WWII trials documenting Nazi atrocities.
Question 5: Which measure of central tendency is most appropriate when data contains extreme outliers?
- Median (Correct answer)
- Mean
- Mode
- Range
Correct answer: Median
The median is the middle value in a data set and is resistant to extreme values (outliers), making it more representative than the mean for skewed distributions.
Question 6: In health research, what is 'selection bias'?
- A systematic error arising from how participants are chosen that makes the study sample unrepresentative (Correct answer)
- The tendency of researchers to select favorable outcomes to report
- Participants choosing which treatment arm to join
- Statistical bias introduced by small sample sizes
Correct answer: A systematic error arising from how participants are chosen that makes the study sample unrepresentative
Selection bias occurs when the process of selecting study participants leads to a sample that does not accurately represent the target population, distorting study conclusions.
BHS Research Methods and Biostatistics 1
In a randomized controlled trial (RCT), what is the primary purpose of randomization?