HSRT Evaluating Scientific Evidence 2 — Questions and Answers
Question 1: A clinical trial reports a relative risk reduction of 50% for a new treatment, but the absolute risk reduction is only 1%. Which statement best reflects the clinical significance?
- The treatment is highly effective based on relative risk alone
- The absolute risk reduction suggests the clinical benefit may be modest (Correct answer)
- Relative and absolute risk reductions always agree in direction
- A 50% relative risk reduction always justifies treatment
Correct answer: The absolute risk reduction suggests the clinical benefit may be modest
An absolute risk reduction of 1% means treating 100 patients prevents one additional case, suggesting the benefit may be modest despite the impressive relative figure.
Question 2: Which component of an evidence hierarchy is typically considered the weakest form of clinical evidence?
- Systematic review
- Randomized controlled trial
- Expert opinion (Correct answer)
- Cohort study
Correct answer: Expert opinion
Expert opinion sits at the bottom of evidence hierarchies because it is most susceptible to individual bias and lacks empirical rigor.
Question 3: A diagnostic test has a sensitivity of 95% and a specificity of 60%. In a population with low disease prevalence, the positive predictive value will be:
- Very high because sensitivity is high
- Very low because prevalence is low (Correct answer)
- Equal to the sensitivity value
- Determined solely by specificity
Correct answer: Very low because prevalence is low
In low-prevalence populations, even highly sensitive tests yield many false positives, resulting in a low positive predictive value.
Question 4: Researchers randomly assign participants to treatment and control groups. The primary purpose of randomization is to:
- Ensure an equal number of males and females
- Control for all known and unknown confounders (Correct answer)
- Guarantee blinding of participants
- Eliminate attrition from the study
Correct answer: Control for all known and unknown confounders
Randomization distributes both known and unknown confounding variables equally across groups, strengthening causal inference.
Question 5: A study is described as 'double-blind.' What does this mean?
- Both the funding agency and the journal are unaware of the results
- Both participants and outcome assessors are unaware of group assignment (Correct answer)
- Two independent researchers conducted the analysis
- The study included two separate blinded control groups
Correct answer: Both participants and outcome assessors are unaware of group assignment
Double-blinding means neither participants nor the researchers assessing outcomes know who received the treatment, reducing performance and detection bias.
Question 6: An article claims that a hospital's new hand-hygiene program reduced infection rates from 10% to 8%. The authors report this as statistically non-significant (p = 0.12). The most reasonable conclusion is:
- The program definitively does not work
- The observed reduction may be due to chance; more data are needed (Correct answer)
- Statistical significance confirms clinical effectiveness
- The p-value proves the null hypothesis is true
Correct answer: The observed reduction may be due to chance; more data are needed
A non-significant p-value does not prove the null hypothesis; it means the data are insufficient to rule out chance as an explanation.
Question 7: Which action is most important when critically appraising a research article's methodology?
- Checking the prestige of the journal it was published in
- Evaluating whether the study design is appropriate for the research question (Correct answer)
- Counting the number of references cited
- Confirming the lead author's institutional affiliation
Correct answer: Evaluating whether the study design is appropriate for the research question
The alignment between the study design and the research question is the foundational step in assessing methodological quality.
HSRT Evaluating Scientific Evidence 2
A clinical trial reports a relative risk reduction of 50% for a new treatment, but the absolute risk reduction is only 1%.
Which statement best reflects the clinical significance?