Re: [R] cch() and coxph() for case-cohort

From: Terry Therneau <therneau_at_mayo.edu>
Date: Mon, 16 Jun 2008 14:21:21 -0500 (CDT)

 I tried to compare if cch() and coxph() can generate same result for same case cohort data

Use the standard data in cch(): nwtco

Since in cch contains the cohort size=4028, while ccoh.data size =1154 after selection, but coxph does not contain info of cohort size=4028.

The rough estimate between coxph() and cch() is same, but the lower and upper CI and P-value are a little different. Can we exactly use coxph() to repeat cch() using with appropriate configuration in coxph()? Is SAS a better way(PHREG,CASECOH.SAS) to implement time-dependent case-cohort?

<output deleted>

----------end included message --------------------


I showed you how to do time-dependent case cohort analysis. Stop complaining and use the advice.  

 No, SAS will not be better. It will be different due to defaults (different convergence criteria, different default ties method). Not better, not worse, just different.  

  The code I sent results in one variance estimate type, the default cch code is another. They are asymptotically equivalent, and in your sample are essentially identical: one CI was (1.497, 2.91) the other (1.491, 2.925). Neither is 'better' or 'correct', both are good. If you feel that you must have the other estimate, then read the paper upon which cch is based (which I wrote); you can find it in the references for the cch help page.   

  The cch output has some default information not in the coxph output and vice versa. So what?   

          Terry Therneau



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