Biostatistics & Study Design USMLE Step 1 Practice Question
A regression model evaluates the effect of obesity on obstructive sleep apnea severity in 250 adults (mean BMI 34 kg/m², apnea-hypopnea index 28 events/hour). Investigators include an obesity × sex interaction term because they suspect the association differs between men and women. Polysomnography confirmed moderate OSA in all participants. No patients used CPAP therapy. Which statistical result would provide the strongest evidence for effect modification by sex?
Answer choices
- AA narrow confidence interval for the intercept
- BA significant interaction term for obesity × sexCorrect answer
- CA large sample size
- DA significant coefficient for obesity alone
- EA significant coefficient for sex alone
- FA significant coefficient for obesity that remains unchanged when sex is added to the model
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