<i>Stage-II</i> estimates of the coefficient for each of the variables (x, y, D) included in the Cox proportional hazard models for different specifications, Monte Carlo simulations, sample size 5000, <i>d</i><sub>1</sub> = 0.2 and <i>δ</i><sub>1</sub> = 0.4.
<p><sup>a</sup><i>z</i><sub>1</sub> is the only instrumental variable, but it is invalid;</p><p><sup>b</sup><i>z</i><sub>1</sub> and <i>z</i><sub>2</sub> are the invalid and valid instrumental variables respectively;</p><p><sup>c</sup><i>z</i><sub>2</sub> is the only instrumental variable, and it is valid. Specification III is correct.</p><p><i>Stage-II</i> estimates of the coefficient for each of the variables (x, y, D) included in the Cox proportional hazard models for different specifications, Monte Carlo simulations, sample size 5000, <i>d</i><sub>1</sub> = 0.2 and <i>δ</i><sub>1</sub> = 0.4.</p
