Biostatistics & Study Design USMLE Step 1 Practice Question
A randomized trial of a new asthma medication in 400 patients shows no difference in FEV1 decline (primary endpoint: -120 mL/year in both groups; p=0.18). Investigators perform 40 unplanned subgroup analyses and report a significant benefit in left-handed women older than 70 years (n=12; p=0.04), with no prior mechanistic hypothesis. Baseline characteristics were balanced between groups. Which statistical problem most directly threatens validity of this subgroup finding?
Answer choices
- AData dredgingCorrect answer
- BLead time bias
- CSpectrum bias
- DConfounding by indication
- EHealthy worker effect
- FType II error due to insufficient statistical power
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