Statistics Research & Evidence-Based Practice 3 — Questions and Answers
Question 1: In evidence-based practice, the PICO framework helps researchers formulate:
- Data analysis procedures
- A well-built clinical question (Correct answer)
- Ethical guidelines for research
- Statistical power calculations
Correct answer: A well-built clinical question
PICO (Population, Intervention, Comparison, Outcome) structures clinical questions to guide systematic literature searches.
Question 2: Which of the following best describes a Type I error?
- Failing to detect a true effect
- Incorrectly rejecting a true null hypothesis (Correct answer)
- Using an inappropriate statistical test
- Reporting a non-significant result as significant after multiple analyses
Correct answer: Incorrectly rejecting a true null hypothesis
A Type I error (false positive) occurs when the null hypothesis is true but is erroneously rejected.
Question 3: An odds ratio of 1.0 in a case-control study indicates:
- A strong positive association
- A strong negative association
- No association between exposure and outcome (Correct answer)
- A statistically significant finding
Correct answer: No association between exposure and outcome
An OR of 1.0 means the odds of the outcome are equal in exposed and unexposed groups, indicating no association.
Question 4: What is the primary advantage of a cohort study over a cross-sectional study?
- It is less expensive to conduct
- It can establish temporal precedence between exposure and outcome (Correct answer)
- It eliminates selection bias entirely
- It does not require a comparison group
Correct answer: It can establish temporal precedence between exposure and outcome
Cohort studies follow participants over time, allowing researchers to confirm that the exposure preceded the outcome.
Question 5: A p-value of 0.03 means:
- There is a 3% probability the null hypothesis is true
- There is a 97% probability the alternative hypothesis is true
- The observed data (or more extreme) would occur 3% of the time if the null hypothesis were true (Correct answer)
- The effect size is clinically meaningful
Correct answer: The observed data (or more extreme) would occur 3% of the time if the null hypothesis were true
The p-value is the probability of obtaining results at least as extreme as observed, assuming the null hypothesis is true.
Question 6: Which bias occurs when subjects with the condition being studied are more likely to remember past exposures than controls?
- Selection bias
- Recall bias (Correct answer)
- Attrition bias
- Hawthorne effect
Correct answer: Recall bias
Recall bias is systematic error due to differences in accuracy or completeness of recollections between cases and controls.
Question 7: When a study reports statistical significance but the effect size is trivially small, this highlights the importance of:
- Increasing the alpha level
- Reporting practical (clinical) significance alongside p-values (Correct answer)
- Using a one-tailed test instead
- Reducing the sample size
Correct answer: Reporting practical (clinical) significance alongside p-values
With large samples even tiny effects reach significance, so practical/clinical significance must be evaluated alongside p-values.
Statistics Research & Evidence-Based Practice 3
In evidence-based practice, the PICO framework helps researchers formulate: