R help - Mar 2011 - Frailty model -- Conditional or Marginal?

Dear all,

When I ran a frailty model like,

model <- coxph(Surv(Day, Indicator) ~ trt + frailty(group,
distribution="gaussian"))

The variance of effect estimate of trt was estimated by conditional model or
marginal model?

Thanks.

Alex

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On Thu, Mar 10, 2011 at 6:33 AM, hongsheng wu <comp611 at gmail.com>
wrote:
> Dear all,
>
> When I ran a frailty model like,
>
> model <- coxph(Surv(Day, Indicator) ~ trt + frailty(group,
> distribution="gaussian"))
>
> The variance of effect estimate of trt was estimated by conditional model
or
> marginal model?
The frailty model is a conditional model, that is, the hazards for
different treatment groups are assumed proportional conditional on the
frailty.

     -thomas

-- 
Thomas Lumley
Professor of Biostatistics
University of Auckland