Biostatistics & Study Design USMLE Step 1 Practice Question
A 52-year-old man with hypertension (BP 168/98 mmHg, HR 88, RR 16, Temp 37.2°C) undergoes evaluation for cardiovascular risk. A regression model predicts systolic blood pressure using body mass index (32 kg/m²), waist circumference (104 cm), and body fat percentage (28%). Each variable individually correlates with blood pressure, but when entered together their coefficients become unstable with markedly elevated standard errors. Recent lipid panel is unremarkable. Which statistical problem best explains this pattern?
Answer choices
- AMulticollinearityCorrect answer
- BHawthorne effect
- CEffect modification
- DDifferential misclassification
- ERight censoring
- FConfounding bias
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