which model should be done when selecting a random variable in the cox proportional hazard model what model does cox proportional hazard use how to do model selection for cox proportional hazards how to do the selection for cox proportional hazards how to perform backward selection in cox proportional hazard when performing backward selection for cox proportional hazards the model is what is the model selection for proportional hazards in cox? why do I perform a backward selection on the cox proportional hazard model why do I do backward selection for models what is the ph for cox proportional hazards when does a model selection for cox hazard which model to test if model is better how to do model selection for cox proportional hazards model what model is a b without stratification how to do a model selection why do cox models require backward selection how to do cox proportional hazards does the cox proportional hazards model have a model selection function why do you use cox proportional hazards which model is used to compare a full model with an explanatory model?