# In a time to event analysis, when is it appropriate to use parametric models to compute restricted means?

Restricted mean is gaining popularity as a substitute for the hazard ratios to compare survival times in time-to-event analysis, especially in observational studies where chances of violation of proportional hazards assumption are higher.

To compute restricted mean, we have two major approaches: 1. Using Kaplan-Meier estimate (non-parametric) 2. Using parametric models like Weibull, Gompertz, LogLog, etc.

Is there a guideline which says when to go for parametric estimates and when to go for non-parametric estimates for computing restricted mean?