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Re: st: re Kaplan-Meier survival analysis model

From   Maarten buis <[email protected]>
To   [email protected]
Subject   Re: st: re Kaplan-Meier survival analysis model
Date   Wed, 23 Jan 2008 10:55:53 +0000 (GMT)

--- Ziad El-Khatib <[email protected]> wrote:
> My understanding to KM survival model is to have the variable related
> to the 'survival' event to be coded as (0: as nothing happened or 1:
> as the event did happen) For example if we are monitoring death: 1)
> died, 0) did not die.
> I am assessing variable for sickness, to see if there is difference
> in time to show between
>   option 1) patients who were sick before treatment and became sicker
> after treatment
>   option 2) patients who were not sick before treatment but became
> sicker after treatment
>  option3) And there are patients who did not show any sickness at
> all.
> would i code them as follow:
> option1 : code 1
> option2: code 2
> option3: code 0

Survival models model the duration till an effent, so that does not
seem to apply in your case. I would suppose that you are interested in
whether or not someone became sicker after treatment, and you want to
control for whether or not someone was already sick. I would create two
sicker: 1) got sicker, 0) not sicker 
sick: 1) was sick, 0) was not sick. 

and than type:
logit sicker sick

Hope this helps,

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

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