Statistics Research & Evidence-Based Practice 4 — Questions and Answers
Question 1: A funnel plot in meta-analysis is asymmetrical. This MOST likely suggests:
- High between-study heterogeneity
- Publication bias or small-study effects (Correct answer)
- Incorrect effect size calculation
- Insufficient statistical power
Correct answer: Publication bias or small-study effects
Asymmetry in a funnel plot often indicates publication bias, where small negative studies are underrepresented.
Question 2: Random assignment in an experiment is MOST important for:
- Ensuring a large enough sample
- Controlling known and unknown confounding variables (Correct answer)
- Blinding participants to treatment
- Improving measurement reliability
Correct answer: Controlling known and unknown confounding variables
Randomization distributes both measured and unmeasured confounders across groups, supporting causal inference.
Question 3: An IRB (Institutional Review Board) primarily ensures that research:
- Achieves statistical significance
- Protects the rights and welfare of human subjects (Correct answer)
- Uses valid and reliable measures
- Obtains a sufficiently large sample
Correct answer: Protects the rights and welfare of human subjects
IRBs evaluate study protocols to protect participants from harm and ensure ethical standards are met.
Question 4: In a regression study, multicollinearity refers to:
- Non-linear relationships between predictors and the outcome
- High correlation among predictor variables, making it difficult to isolate their individual effects (Correct answer)
- Heteroscedasticity in the residuals
- Measurement error in the outcome variable
Correct answer: High correlation among predictor variables, making it difficult to isolate their individual effects
Multicollinearity occurs when predictors are highly correlated, inflating standard errors and destabilizing coefficient estimates.
Question 5: Which level of the evidence hierarchy is LOWEST?
- Systematic reviews with meta-analysis
- Randomized controlled trials
- Expert opinion and case reports (Correct answer)
- Well-designed cohort studies
Correct answer: Expert opinion and case reports
Expert opinion and case reports sit at the bottom of the evidence pyramid because they are most susceptible to bias.
Question 6: The concept of 'statistical power' is defined as:
- The probability of committing a Type I error
- The probability of correctly rejecting the null hypothesis when it is false (Correct answer)
- The width of the confidence interval
- The ratio of effect size to standard deviation
Correct answer: The probability of correctly rejecting the null hypothesis when it is false
Power (1 − β) is the probability of detecting a true effect, and is influenced by sample size, effect size, and alpha.
Question 7: Which of the following is an example of confounding in an observational study?
- Participants who drop out have worse outcomes than completers
- Coffee drinkers have higher rates of lung cancer because they also smoke more (Correct answer)
- Researchers know which group participants are in
- The outcome measure has low test-retest reliability
Correct answer: Coffee drinkers have higher rates of lung cancer because they also smoke more
Smoking is a confounder because it is associated with both coffee drinking and lung cancer, creating a spurious association.
Statistics Research & Evidence-Based Practice 4
A funnel plot in meta-analysis is asymmetrical.
This MOST likely suggests: