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Re: st: Comparison in survival analysis


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Comparison in survival analysis
Date   Sun, 26 Aug 2007 18:13:35 +0100 (BST)

Given your earlier posts I am guessing that you have no slope at all.
All you got is a constant and a shape parameter. The shape is
parameterized differently in the weibull and the log logistic, so it is
very hard to compare them. Just comparing the numerical values of these
paramterers is completely misleading, the numbers could be completely
different and still convey very similar substantive information, or
vice versa. 

We may be able to give you more helpful advise if you tell us exactly
what you typed, which parameters you are comparing (neither log
logistic or the weibull report an alpha or a beta) and what you want to
use those parameters for.

-- Maarten

--- khan ali <economichust@yahoo.com> wrote:
> For the same data set,the estimated parameters(two
> parametrs,alpha and beta(slope)) by weibull and
> loglogistic models narrate a different story(having
> different signs).How do the parameters of two
> distribiutions can be compared?
> 
> The generalized weibull of Mudholkar,et al.(1996)
> provides much greater flexibilty at the expense of an
> additional shape parameter(having two shape parameters
> and in total three parameters).How do we can estimate
> this three parameter weibull distribution.


-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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