I am trying to use two variables - activity score (ascore - a whole number indicating amount of activity) and gini (given by Gini-Simpson index - a value ranging between 0 and 1, indicating diversity of activity) to predict number of days they survived.
Call: coxph(formula = Surv(NumDays, failed) ~ ascore + gini, data = records1) n= 47966, number of events= 39853 coef exp(coef) se(coef) z Pr(>|z|) ascore -2.801e-03 9.972e-01 5.634e-05 -49.72 <2e-16 *** gini -2.535e-01 7.761e-01 2.229e-02 -11.38 <2e-16 *** --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 exp(coef) exp(-coef) lower .95 upper .95 ascore 0.9972 1.003 0.9971 0.9973 gini 0.7761 1.289 0.7429 0.8107 Concordance= 0.648 (se = 0.003 ) Rsquare= 0.068 (max possible= 1 ) Likelihood ratio test= 3358 on 2 df, p=0 Wald test = 2702 on 2 df, p=0 Score (logrank) test = 2705 on 2 df, p=0
If my understanding of the above model is right, what this is saying is holding the other covariate constant, one additional activity reduces the hazard of animal dying by a factor of exp(ascore) = 0.9972 on an average that is by 0.28 percent while a unit of diversity(gini) causes a reduction in the hazard of animal dying by a factor of exp(ead) = 0.7761 on an average that is by 25.35 percent.
Now a unit of activity is easily understandable to be 1 additional activity. But what does unit of diversity mean when I take gini which ranges from 0 to 1? So, what does a one unit rise in Gini-Simpson indicate? Also, how do I define what the original hazard is based on my model?