[R] OOT: frailty-multinivel
tlumley at u.washington.edu
Wed Nov 24 18:00:11 CET 2004
On Wed, 24 Nov 2004, Kjetil Brinchmann Halvorsen wrote:
> 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
> 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.
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