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Noninferiority trial — USMLE Step 3 MCQ

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HardPreventive Medicine, Epidemiology, BiostatisticsNoninferiority trialUSMLE Step 3

A trial compares a shorter antibiotic course with standard therapy. The confidence interval for the difference in cure rates lies entirely above the prespecified noninferiority margin and crosses zero. The shorter course has fewer adverse effects. Which of the following is the most likely explanation for this patient's findings?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — The shorter course is noninferior but not proven superior

For noninferiority, the confidence interval must exclude clinically unacceptable loss of efficacy; crossing zero means superiority is not demonstrated.

Reference: CONSORT extension for noninferiority trials; USMLE Step 3 biostatistics content outline