[R] survreg: fitting different location parameters
Göran Broström
gb at tal.stat.umu.se
Mon Jan 24 13:49:09 CET 2005
On Sun, Jan 23, 2005 at 03:10:18PM -0500, h.brunschwig at utoronto.ca wrote:
> Hi R-Help!
>
> My question: I have lifetime/failure data of machines with different
> stress levels and i think an weibull/extreme value distribution would
> fit this data. So I did:
>
> model1 <- survreg(Surv(lfailure)~stress,data=steel,dist="extreme")
>
> (where lfailure=log(failure))
>
> Now I would like to do a likelihood ratio test to test the hypothesis
>
> H0: location parameters of the extreme value distribution are equal
> for each stress level.
>
> So in order to perform the likelihood ratio test I need the likelood
> of the model under
>
> HA: location parameters are not equal (i.e. each stress level has its
> slope and intercept).
>
> How can I do this?
Stratify on stress level.
--
Göran Broström tel: +46 90 786 5223
Department of Statistics fax: +46 90 786 6614
Umeå University http://www.stat.umu.se/egna/gb/
SE-90187 Umeå, Sweden e-mail: gb at stat.umu.se
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