I need to use parametric models to model survival data. If the PH assumption holds, I would fit the data for my two intervention groups using a single covariate for treatment effect.
I fit a Cox PH model to my unstratified data and the PH assumption seems violated (scaled Schoenfeld residuals test: p=0.001).
Can I at this point state that the PH assumption is violated and must use stratified parametric models (e.g. log-logistic, generalised gamma)? Or the test performed is specific to the Cox model and does not apply to other (fully parametric) models?
Note that the only covariate in the models is the treatment effect.