ATC Evidence-Based Practice 3 — Questions and Answers
Question 1: A clinician calculates an NNT of 4 for a new ankle rehabilitation protocol. This means:
- 4 patients will experience adverse effects
- 4 patients must be treated for one additional patient to benefit (Correct answer)
- The protocol is 4 times more effective than placebo
- Only 4 sessions are needed for recovery
Correct answer: 4 patients must be treated for one additional patient to benefit
Number Needed to Treat (NNT) represents how many patients must receive the treatment for one additional patient to achieve a beneficial outcome.
Question 2: Which bias occurs when participants or researchers know the treatment group assignment in a clinical trial?
- Selection bias
- Performance bias (Correct answer)
- Attrition bias
- Detection bias
Correct answer: Performance bias
Performance bias occurs when knowledge of group allocation influences how care is provided or how participants behave during the study.
Question 3: An athletic trainer wants to assess the reproducibility of a measurement tool across different testers. Which statistical measure is most appropriate?
- Pearson correlation coefficient
- Intraclass correlation coefficient (ICC) (Correct answer)
- Cohen's kappa
- Standard error of measurement
Correct answer: Intraclass correlation coefficient (ICC)
The ICC is the preferred statistic for assessing inter-rater and intra-rater reliability of continuous measurements.
Question 4: In a clinical study, the control group receives a sham ultrasound treatment. This is an example of:
- Stratified randomization
- Placebo control (Correct answer)
- Crossover design
- Allocation concealment
Correct answer: Placebo control
A sham treatment mimics the real intervention without the active component, serving as a placebo control to isolate treatment effects.
Question 5: Which level of evidence in most hierarchies ranks expert opinion without critical appraisal?
- Level I
- Level II
- Level IV
- Level V (Correct answer)
Correct answer: Level V
Expert opinion without critical appraisal or based solely on experience is typically ranked at the lowest level (Level V) of evidence hierarchies.
Question 6: When a study reports a 95% confidence interval that does NOT cross 1.0 for a relative risk, this suggests:
- The result is not statistically significant
- The result is statistically significant (Correct answer)
- The sample size was too small
- The study had high attrition
Correct answer: The result is statistically significant
A 95% CI for relative risk that does not include 1.0 indicates a statistically significant difference between groups at the 0.05 alpha level.
Question 7: Which type of study is most appropriate for determining the prevalence of a condition in a population at a single point in time?
- Longitudinal cohort study
- Cross-sectional study (Correct answer)
- Case-control study
- Randomized controlled trial
Correct answer: Cross-sectional study
Cross-sectional studies measure the prevalence of disease or characteristics in a population at a single point in time.
ATC Evidence-Based Practice 3
A clinician calculates an NNT of 4 for a new ankle rehabilitation protocol.
This means: