Biostatistics & Study Design USMLE Step 1 Practice Question
A 58-year-old man with type 2 diabetes (HbA1c 9.2%, fasting glucose 187 mg/dL) presents for cost analysis study enrollment. Linear regression models his HbA1c versus annual healthcare expenditure. Residual plots reveal heteroscedasticity: residual spread is minimal at predicted costs below $5,000 but progressively widens at costs exceeding $15,000. Blood pressure is 138/86 mmHg; no acute complications noted. Which regression assumption violation does this finding most strongly suggest?
Answer choices
- AMulticollinearity
- BHeteroscedasticityCorrect answer
- CSelection bias
- DInteraction
- EConfounding by indication
- FNon-linearity between HbA1c and healthcare expenditure
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