Hello,
I am running Cox regression and wanted to test effect modification across race (4 strata). This is the code I am using:
proc phreg data = ABC;
model asthmatt*asthma(0) = p_cvscore tp_cvscore/risklimit;
tp_cvscore=p_cvscore*log(asthmatt);
test_proportionality: test p_cvscore, tp_cvscore;
run;
Is testing for effect modification the same for proportionality assumption? I need explanation and if my code correct or wrong, please. Assuming the test is approriate in this case, what other options to use if the test of proportionality was sig? I mean what to do, what statistical solutions should I proceed with?
Thanks,