PROC PHREG DATA = my_data
CLASS industry_code
MODEL (tstart, tstop)*endpt(0) = treatment_variable industry_code/ TIES = EFRON RL;
RUN;
@chris2377 wrote:My questions are as follows:1. Do I understand correctly that I don't have to verify the PH assumption prior to estimating the model?
The answer to the first question is "No, you should verify the PH assumption". I am not sure of the underlying rationale of imposing a time-dependent variable on the Cox model. If you do not reject the PH assumption, then it is statistically plausible to get rid of the time-dependent variable.
@chris2377 wrote:3. Are the ways to asses goodness of fit the same for models with time-dependent covariates and "standard" PH models? Can use the statistics produced by the phreg or I need to adjust them somehow to account for using counting process syntax?
See this dissertation for more details: Evaluation of Goodness-of-fit Tests for the Cox Proportional Hazards Model with Time-Varying Covaria....
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