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Confidence interval — FRCA Primary MCQ

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HardStatisticsConfidence intervalFRCA Primary

A superiority trial reports a mean pain-score difference of 1.2 points with a 95% confidence interval from 0.4 to 2.0; the prespecified minimum clinically important difference is 1.5. Which conclusion is best?

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Correct answer: C — The effect is statistically significant, but clinical importance remains uncertain

The best answer is “The effect is statistically significant, but clinical importance remains uncertain”. The confidence interval excludes zero, supporting a statistically detectable effect, but it spans the 1.5-point clinical threshold. The true effect may therefore be smaller or larger than the minimum clinically important difference. Superiority data do not establish equivalence or non-inferiority without a prespecified design and margin.

Reference: Ranganathan et al., Equivalence trials: https://pmc.ncbi.nlm.nih.gov/articles/PMC9106130/