Stata: Data Analysis and Statistical Software

TCATOG2 is the categorical variable which violates the proportional hazards assumption. This is a tabulation of the variable:

. tab TCATOG2

     STAGE: |
     1=pTa; |
     2=pT1; |
   3=T2-T4  |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        658       50.62       50.62
          2 |        291       22.38       73.00
          3 |        351       27.00      100.00
------------+-----------------------------------
      Total |      1,300      100.00

value 1 are early tumours with better survival and are clearly masking the effect of later stage (value 3) tumours.

Should I create new dummy variables, test each for proportional hazards and re-write the model based upon this? I'm not sure how I should code up any new variables I create.

Best wishes

Tim


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