STP Research Methods 3 — Questions and Answers
Question 1: In a double-blind randomized controlled trial, who is unaware of the treatment allocation?
- Only the participant
- Only the researcher
- Both the participant and the researcher administering/assessing the treatment (Correct answer)
- The ethics committee and the statistician
Correct answer: Both the participant and the researcher administering/assessing the treatment
In a double-blind design, both the participant and the researcher interacting with or assessing them are unaware of group allocation to reduce bias.
Question 2: Which measure of central tendency is LEAST affected by extreme outliers in a dataset?
- Mean
- Mode
- Variance
- Median (Correct answer)
Correct answer: Median
The median is the middle value of a ranked dataset and is not influenced by extreme high or low values, unlike the mean.
Question 3: A researcher reports a 95% confidence interval of 1.2–3.4 for an odds ratio. What can be concluded?
- The result is statistically significant at p<0.05 because the interval excludes 1 (Correct answer)
- The true odds ratio is definitely 2.3
- The result is not statistically significant because the interval is wide
- The p-value is exactly 0.05
Correct answer: The result is statistically significant at p<0.05 because the interval excludes 1
Because the 95% confidence interval for an odds ratio does not include 1 (the null value), the result is statistically significant at the 0.05 level.
Question 4: Ecological fallacy occurs when:
- Individual-level conclusions are incorrectly drawn from group-level data (Correct answer)
- A study fails to recruit enough participants
- Data from different time periods are compared
- Multiple statistical tests inflate the false-positive rate
Correct answer: Individual-level conclusions are incorrectly drawn from group-level data
Ecological fallacy is the error of applying associations found at the group level to individuals, which may not hold for any given person.
Question 5: Which type of error occurs when a researcher concludes there IS an effect when in reality there is none?
- Type II error
- Sampling error
- Type I error (Correct answer)
- Measurement error
Correct answer: Type I error
A Type I error (false positive) is rejecting a true null hypothesis — concluding an effect exists when it does not.
Question 6: Allocation concealment in an RCT is primarily used to prevent:
- Participant dropout
- Selection bias during assignment to treatment groups (Correct answer)
- Measurement bias in outcome assessment
- Publication bias
Correct answer: Selection bias during assignment to treatment groups
Allocation concealment hides the upcoming treatment assignment from those enrolling participants, preventing selection bias before randomization.
Question 7: The number needed to treat (NNT) is calculated as:
- 1 divided by the relative risk
- 1 divided by the absolute risk reduction (Correct answer)
- Absolute risk reduction divided by relative risk
- Relative risk reduction minus absolute risk reduction
Correct answer: 1 divided by the absolute risk reduction
NNT = 1 / Absolute Risk Reduction, expressing how many patients must be treated to prevent one additional bad outcome.
STP Research Methods 3
In a double-blind randomized controlled trial, who is unaware of the treatment allocation?