CRE CRE Research & Evidence-Based Practice 2 — Questions and Answers
Question 1: A 95% confidence interval in a clinical study represents:
- The range within which the true population value likely falls (Correct answer)
- The percentage of studies that agree with the finding
- The probability that the study design was flawless
- The acceptable margin of measurement error
Correct answer: The range within which the true population value likely falls
A 95% confidence interval indicates the range within which the true population parameter would fall in 95 of 100 repeated experiments.
Question 2: The primary purpose of a control group in a randomized clinical trial is to:
- Allow testing of multiple interventions simultaneously
- Provide a comparison baseline for the experimental intervention (Correct answer)
- Include patients with the most severe presentation
- Eliminate the need for statistical analysis
Correct answer: Provide a comparison baseline for the experimental intervention
The control group receives no intervention or standard care, providing the baseline needed to determine whether the experimental treatment causes observed changes.
Question 3: 'Number needed to treat' (NNT) in clinical research describes:
- The average number of doses a patient requires per day
- How many patients must be treated for one additional patient to benefit (Correct answer)
- The minimum sample size for statistical significance
- The number of replication trials required to confirm results
Correct answer: How many patients must be treated for one additional patient to benefit
NNT is calculated as the inverse of absolute risk reduction and tells clinicians how many patients must receive treatment for one to gain benefit.
Question 4: In spirometry, an FEV1/FVC ratio below which threshold confirms the presence of airflow obstruction?
- 0.50
- 0.60
- 0.70 (Correct answer)
- 0.80
Correct answer: 0.70
A post-bronchodilator FEV1/FVC ratio below 0.70 is the GOLD-defined diagnostic criterion for airflow obstruction in COPD.
Question 5: Which type of bias occurs when participants who drop out of a study differ systematically from those who complete it?
- Selection bias
- Recall bias
- Attrition bias (Correct answer)
- Confirmation bias
Correct answer: Attrition bias
Attrition bias arises when dropout is non-random and the characteristics of completers differ from non-completers, distorting study results.
Question 6: A meta-analysis synthesizes data from multiple studies primarily to:
- Confirm a single landmark study's findings
- Increase statistical power and precision of effect estimates (Correct answer)
- Demonstrate that further research is unnecessary
- Replace existing clinical practice guidelines
Correct answer: Increase statistical power and precision of effect estimates
Meta-analysis pools individual study results to increase total sample size and statistical power, yielding more precise estimates of treatment effects.
CRE CRE Research & Evidence-Based Practice 2
A 95% confidence interval in a clinical study represents: