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RE: st: RE: Weibull simulation-parametrization


From   "Nick Cox" <[email protected]>
To   <[email protected]>
Subject   RE: st: RE: Weibull simulation-parametrization
Date   Wed, 7 May 2003 13:39:00 +0100

Nikos Padazis
 
> Thanx to Antoine and Nick for their useful responses
> and code. As far as it concerns the Weibull p.d.f. I
> just copied the formula from D. Collett's book
> "Modelling survival data in medical research" page
> 110.

The formula you copied from Collett was in effect 

p.d.f. :
f(t)=lambda*gamma*t^(gamma-1)*exp(-lambda*t^gamma)

The price of this formula is, 
so far as I can see, complicated dimensions 
and therefore units for the scale parameter
lambda. 

You can see the consequence in Collett's 
formula for the mean on p.111. 

I'll record a preference for parameterisations 
which allow parameters to be assigned units 
easily. 

Nick 
[email protected] 

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