[R] survreg: fitting different location parameters

2005-01-24 Thread Hadassa Brunschwig
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? 

Thanks for any help!

Hadassa

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[R] survreg: fitting different location parameters

2005-01-24 Thread h . brunschwig
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?

Thanks for any help!

Hadassa

__
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[R] survreg: fitting different location parameters

2005-01-24 Thread h . brunschwig
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? 

Thanks for any help! 

Hadassa

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Re: [R] survreg: fitting different location parameters

2005-01-24 Thread Göran Broström
On Sun, Jan 23, 2005 at 03:10:18PM -0500, [EMAIL PROTECTED] 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 Broströmtel: +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: [EMAIL PROTECTED]

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Re: [R] survreg: fitting different location parameters

2005-01-24 Thread h . brunschwig
I am still trying to find a common intercept but a different slopes for each 
group within my lifetime data. By stratifying the variable stress (the groups) 
I get different scale parameters which is not my goal.
So I did this:

survreg(Surv(lfailure)~as.factor(stress),data=steel,dist=extreme)

and I did get different slopes but common intercepts and scales.
Is this correct? I am a bit unsure as I did it with a different software and 
got different estimates...

Thanks for any help

Hadassa





Quoting Göran Broström [EMAIL PROTECTED]:

 On Sun, Jan 23, 2005 at 03:10:18PM -0500, [EMAIL PROTECTED] 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 Broströmtel: +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: [EMAIL PROTECTED]


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