CBIS Research Methods and Evidence 2 — Questions and Answers
Question 1: In a randomized controlled trial (RCT) studying TBI rehabilitation, what is the PRIMARY purpose of the control group?
- To receive a placebo intervention
- To provide a comparison baseline against which treatment effects are measured (Correct answer)
- To reduce the overall sample size needed
- To allow researchers to test multiple interventions simultaneously
Correct answer: To provide a comparison baseline against which treatment effects are measured
The control group provides a baseline comparison so researchers can attribute observed changes to the treatment rather than natural recovery or other factors.
Question 2: Which statistical measure best describes the spread of individual data points around the mean in a TBI outcome study?
- Median
- Mode
- Standard deviation (Correct answer)
- Interquartile range
Correct answer: Standard deviation
Standard deviation quantifies the average distance of individual data points from the mean, reflecting variability within the dataset.
Question 3: A CBIS researcher finds a p-value of 0.03 in a study on cognitive rehabilitation. What does this indicate?
- There is a 3% chance the intervention worked
- There is a 3% probability of observing these results if the null hypothesis were true (Correct answer)
- The effect size is clinically meaningful
- The study has 97% statistical power
Correct answer: There is a 3% probability of observing these results if the null hypothesis were true
A p-value of 0.03 means there is a 3% probability of obtaining the observed results (or more extreme) assuming the null hypothesis is true.
Question 4: Which study design is MOST appropriate for determining the incidence of post-TBI depression in a defined population over 12 months?
- Cross-sectional survey
- Prospective cohort study (Correct answer)
- Case-control study
- Single-case experimental design
Correct answer: Prospective cohort study
A prospective cohort study follows a defined population forward in time, allowing calculation of new case incidence rates.
Question 5: In TBI research, 'blinding' of outcome assessors is intended to reduce which type of bias?
- Selection bias
- Attrition bias
- Detection bias (Correct answer)
- Confounding bias
Correct answer: Detection bias
Detection (or ascertainment) bias occurs when knowledge of treatment allocation influences how outcomes are measured; blinding assessors prevents this.
Question 6: A meta-analysis of TBI memory interventions includes a funnel plot. Asymmetry in the funnel plot most likely indicates:
- Heterogeneity in participant characteristics
- Publication bias favoring positive results (Correct answer)
- Inadequate sample sizes in all studies
- Inconsistent outcome measurement tools
Correct answer: Publication bias favoring positive results
Funnel plot asymmetry in meta-analyses is a common indicator of publication bias, where studies with positive results are more likely to be published.
Question 7: Which level of evidence in the hierarchy is typically assigned to a well-conducted systematic review of RCTs?
- Level I (Correct answer)
- Level II
- Level III
- Level IV
Correct answer: Level I
Systematic reviews of multiple well-designed RCTs occupy Level I (the highest level) in most evidence hierarchies used in clinical practice.
CBIS Research Methods and Evidence 2
In a randomized controlled trial (RCT) studying TBI rehabilitation, what is the PRIMARY purpose of the control group?