RDN Research and Evidence-Based Practice 1 — Questions and Answers
Question 1: A systematic review with meta-analysis is considered which level of evidence in evidence-based dietetics practice?
- Level I — the highest level of evidence (Correct answer)
- Level II evidence
- Level III evidence
- Level IV — the lowest level of evidence
Correct answer: Level I — the highest level of evidence
Systematic reviews with meta-analyses represent Level I evidence, the highest quality in evidence-based practice hierarchies, because they synthesize data from multiple high-quality studies.
Question 2: In a randomized controlled trial (RCT), what is the PRIMARY purpose of randomization?
- To reduce study costs and duration
- To eliminate selection bias and ensure group comparability (Correct answer)
- To increase the overall sample size
- To blind participants to their treatment assignment
Correct answer: To eliminate selection bias and ensure group comparability
Randomization distributes known and unknown confounders equally between groups, reducing selection bias and ensuring the groups are comparable at baseline.
Question 3: A study reports a p-value of 0.03. This BEST indicates that:
- The results are clinically significant and meaningful
- There is a 3% probability the observed results occurred by chance alone if the null hypothesis is true (Correct answer)
- The null hypothesis is accepted
- The effect size observed in the study is large
Correct answer: There is a 3% probability the observed results occurred by chance alone if the null hypothesis is true
A p-value of 0.03 means there is a 3% probability of obtaining the observed results (or more extreme) if the null hypothesis were true, indicating statistical significance at the 0.05 level.
Question 4: A 95% confidence interval for a relative risk is reported as 1.2–3.4. This means:
- The true value falls outside this range 95% of the time
- We are 95% confident the true relative risk lies between 1.2 and 3.4 (Correct answer)
- The result is not statistically significant because 1.0 is excluded
- The study had a 5% measurement error rate
Correct answer: We are 95% confident the true relative risk lies between 1.2 and 3.4
A 95% confidence interval means that if the study were repeated 100 times, approximately 95 of the resulting intervals would contain the true population parameter.
Question 5: A malnutrition screening tool has high sensitivity. This PRIMARILY means the tool:
- Correctly identifies most people WITHOUT malnutrition (high true negative rate)
- Has a very low false positive rate
- Correctly identifies most people WITH malnutrition (high true positive rate) (Correct answer)
- Is also highly specific
Correct answer: Correctly identifies most people WITH malnutrition (high true positive rate)
Sensitivity is the ability of a test to correctly identify true positives — in this case, patients who actually have malnutrition.
Question 6: Which study design is BEST suited to establish a causal relationship between a dietary pattern and disease?
- Cross-sectional study
- Case-control study
- Randomized controlled trial (Correct answer)
- Ecological study
Correct answer: Randomized controlled trial
RCTs are the gold standard for establishing causality because randomization controls for confounding variables, allowing true cause-and-effect relationships to be determined.
Question 7: Publication bias in nutrition research MOST often refers to:
- Bias introduced when authors publish under pen names
- The tendency for journals to preferentially publish positive or statistically significant findings (Correct answer)
- Errors in the bibliographic references of published studies
- Restricting publications to only high-impact-factor journals
Correct answer: The tendency for journals to preferentially publish positive or statistically significant findings
Publication bias occurs when studies with positive or statistically significant results are more likely to be published than those with null or negative results, skewing the available evidence base.
RDN Research and Evidence-Based Practice 1
A systematic review with meta-analysis is considered which level of evidence in evidence-based dietetics practice?