Addition of a cluster() term fits a Generalized Estimating Equations
(GEE) type of model, addition of frailty() fits a random effects model
(Mixed Effect or ME). In glm analysis (linear regression, logistic
regression, etc) the arguments about the advantages/disadvantages of GEE
ve ME would
Dear List,
Can anyone please explain the difference between cluster() and
frailty() in a coxph? I am a bit puzzled about it. Would appreciate
any useful reference or direction.
cheers,
Ehsan
marginal.model - coxph(Surv(time, status) ~ rx + cluster(litter), rats)
frailty.model -
Hi Ehsan,
My understanding (hopefully someone will jump in if this is wrong) is
that cluster() identifies a variable that is an indicator for
correlated observations (rats in a litter, children in a classroom,
etc.). The relative risk from treatment (rx) is for a random sample
of rats.
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