Hi,
I would like to ask two questions for the cox regression model.
1. If I use chronological age as the time scale, can I use the entering age as the covariate in the model at the same time? Is it wrong if I use age as the time scale and adjust it as the covariate in one cox model simultaneously?
2. When time-varing covariates existed, we could use either tvc() or strata() options to deal with this problem, are they exchangable in terms of ultilization? I mean, which method is better to deal with the time-varing covariates? because we were taught that stratification could be used for multi-center studies, or clustered data, or matched data, and should not be done for the covariates of interest. So I feel confused when to use tvc or strata in the cox regression model.
Thanks very much if anyone could reply.
I would like to ask two questions for the cox regression model.
1. If I use chronological age as the time scale, can I use the entering age as the covariate in the model at the same time? Is it wrong if I use age as the time scale and adjust it as the covariate in one cox model simultaneously?
2. When time-varing covariates existed, we could use either tvc() or strata() options to deal with this problem, are they exchangable in terms of ultilization? I mean, which method is better to deal with the time-varing covariates? because we were taught that stratification could be used for multi-center studies, or clustered data, or matched data, and should not be done for the covariates of interest. So I feel confused when to use tvc or strata in the cox regression model.
Thanks very much if anyone could reply.
