Watson-Glaser Critical Thinking Appraisal Interpreting Evidence and Data Questions and Answers 5

Question 1

A clinical trial reports that a new drug reduced symptoms in 40% of patients compared to 30% on placebo. The p-value is 0.04. What is the most accurate interpretation?

Accepted Answer

The result is statistically significant, suggesting the difference is unlikely due to chance, though clinical importance should also be assessed

Answer

Statistical significance at p<0.05 indicates the result is unlikely to be random chance, but clinical significance (the size and practical value of the effect) must also be evaluated.

Question 2

A graph shows violent crime falling every year for a decade. A politician says 'our new policing program, launched 2 years ago, is working.' What is the key interpretive issue?

Accepted Answer

Crime was already declining before the program started, so attributing the trend to the program is premature

Answer

The pre-existing downward trend existed before the intervention, making it impossible to credit the program without isolating its specific effect.

Question 3

A study finds that people who floss daily have fewer heart attacks. Before concluding flossing protects the heart, what must be considered?

Accepted Answer

People who floss daily may share other health habits that reduce heart attack risk

Answer

Daily flossing may be a marker of overall health-consciousness, meaning better diet, exercise, and other habits — not flossing itself — could explain the outcome.

Question 4

A report states that School X's test scores improved 20 points after adopting a new curriculum. However, 30% of the lowest-scoring students transferred out that year. What does this suggest?

Accepted Answer

The score increase may be partly or entirely explained by a change in the student population, not the curriculum

Answer

When lower-performing students leave a group, average scores rise mechanically — this is sometimes called compositional change or a selection effect.

Question 5

A researcher publishes data showing a positive result. Ten other teams tested the same hypothesis and found no effect, but did not publish. What problem does this illustrate?

Accepted Answer

Publication bias, where positive results are more likely to be published, making the evidence base misleadingly favorable

Answer

Publication bias skews the literature toward positive findings, making interventions appear more effective than the full body of evidence would support.

Watson-Glaser Critical Thinking Appraisal Practice Test

Watson-Glaser Critical Thinking Appraisal Practice Test

Watson-Glaser Critical Thinking Appraisal Interpreting Evidence and Data Questions and Answers 5