Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
From | Sanam P <sanamp25@yahoo.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | st: Proportional hazard assumption for interaction term |
Date | Mon, 24 May 2010 05:22:34 -0700 (PDT) |
Dear Statalist I was wondering if in the Cox model there is interaction between two categorical variables (here thincat and yearcat), when checking the proportional hazard assumption using : "estat phtest,rank detail" after the model, for the interaction term and the variables involved in interaction to be proportional, should all the terms involved in the interaction be unsignificant? if only one of the main effects at reference value of the other variable involved in the interaction term is significant and all other terms involved in the interaction are not significant, does it still mean that variable is not proportional? is the interaction proportional? (thincat=99 is a category with missing thincat values) Thank you very much in advance, Sanam Time: Rank(t) ---------------------------------------------------------------- | rho chi2 df Prob>chi2 ------------+--------------------------------------------------- _Ithincat~2| 0.00850 0.38 1 0.5365 _Ithincat~3| 0.00776 0.32 1 0.5725 _Ithincat~4| -0.01565 1.30 1 0.2546 _Ithincat~5| -0.04559 11.07 1 0.0009 _Ithinca~99| -0.04752 11.73 1 0.0006 _Iyearcat_2 | -0.00202 0.02 1 0.8835 _Iyearcat_3 | 0.00318 0.05 1 0.8179 _Iyearcat_4 | -0.00582 0.18 1 0.6727 _IthiXye~2_2| -0.00935 0.46 1 0.4964 _IthiXye~2_3| -0.00543 0.16 1 0.6928 _IthiXye~2_4| 0.00142 0.01 1 0.9179 _IthiXye~3_2| -0.00478 0.12 1 0.7281 _IthiXye~3_3| -0.00690 0.25 1 0.6158 _IthiXye~3_4| -0.00593 0.19 1 0.6659 _IthiXye~4_2| -0.00334 0.06 1 0.8081 _IthiXye~4_3| -0.00142 0.01 1 0.9177 _IthiXye~4_4| 0.00910 0.44 1 0.5083 _IthiXye~5_2| 0.00079 0.00 1 0.9543 _IthiXye~5_3| 0.01261 0.84 1 0.3594 _IthiXye~5_4| 0.01758 1.63 1 0.2013 _IthiXye~9_2| 0.00488 0.13 1 0.7229 _IthiXye~9_3| 0.01125 0.67 1 0.4141 _IthiXye~9_4| 0.02605 3.58 1 0.0584 _Istage_2 | -0.07686 33.18 1 0.0000 _Istage_3 | -0.12396 82.46 1 0.0000 _Istage_99 | -0.01765 1.65 1 0.1995 _Ihepcat_2 | -0.02429 3.22 1 0.0727 _Ihepcat_3 | 0.02983 4.73 1 0.0296 _Ihepcat_4 | -0.02254 2.58 1 0.1085 _Ihepcat_5 | 0.03376 6.11 1 0.0135 _Ihepcat_6 | 0.01624 1.43 1 0.2324 _Ihepcat_7 | 0.00075 0.00 1 0.9562 _Isitecat_2 | -0.02876 4.56 1 0.0327 _Isitecat_3 | -0.02031 2.24 1 0.1345 _Isitecat_4 | -0.01405 1.09 1 0.2973 _Isitecat_5 | -0.11526 65.59 1 0.0000 _Isexcat_1 | 0.01412 1.08 1 0.2979 _Iseason_2 | 0.01397 1.03 1 0.3092 _Iseason_3 | 0.00282 0.04 1 0.8368 _Iseason_4 | 0.02057 2.24 1 0.1344 agecatf | -0.00911 0.49 1 0.4843 ------------+--------------------------------------------------- global test | 976.68 41 0.0000 ---------------------------------------------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/