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Data Collectionhard
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A randomized controlled trial compares pain management methods A and B in 100 patients (50 per arm). Baseline pain (covariate X) is balanced due to randomization. Summary statistics:

  • Group A: Pre-pain mean = 7.2, Post-pain mean = 2.8
  • Group B: Pre-pain mean = 7.1, Post-pain mean = 3.5
  • Pooled regression slope (baseline → post, both groups): b=0.42b = 0.42b=0.42
  • Residual variance (within groups): σe2=4.5\sigma^2_e = 4.5σe2​=4.5

Using ANCOVA to adjust for baseline pain, which statements are correct?