OOT: frailty-multinivel

Hola!

I started to search for information about multilevel survival models, and
found frailty in R. This seems to be something of the same, is it the same?

More or less. "Shared frailty" models are the same as hierarchical/mixed 
survival models.  R uses a fitting method that is equivalent to maximum 
likelihood only when exp(random effects) has a Gamma distribution.  The 
"survival" package can fit random intercept models; the new "kinship" 
package fits much more general mixed models.

[I will put in my usual objection to the term "multilevel model"
being used to refer solely to models that include unmeasured 
variables]

Then: why the name frailty (weekness?)

The idea is that 'weaker' individuals fail earlier than `stronger' 
individuals for the same values of covariates.  The concept has been used 
both for modelling correlation between survival times and to motivate 
parametric models that give an initially decreasing hazard.  I have a 
vague impression that the term originated in Scandinavia somewhere.


 	-thomas