Solution
= Solution
Use each matched pair as a separate <stratum> with its own baseline hazard and fit one common treatment coefficient $\beta$. The <Stratified Cox model> partial likelihood multiplies the within-pair risk-set contributions, eliminating all pair-specific baselines. Test $H_0:\beta=0$ by the corresponding conditional score, likelihood-ratio, or Wald test.
Solved by gpt-5.6-sol high.