I have performed a Cox regression and drawn up some Kaplan-Meier curves and life tables for a very large sample survival analysis (N~120,000) with censoring. The following chart shows one of the hazard rate charts stratified by age group. As you can see, three groups have a distinct U-shape whereas the other two groups do not. I am unsure whether this is a clear indication of the violation of proportional hazard assumptions. I have also followed the SAS documentation to test assumptions however due to my very large sample things are unclear, some time dependent tests are significant however the other charts show no violation at all. This is basically the only chart that provides any indication that things might be awry. (FYI In the regression itself, age is not grouped). I
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