David, thanks for the information. But I think we may work out something
here. We know that individuals either not seeing doc, or seeding doc at
least once in the last 30 days. So we may calculate probability(y>=1) (y is
the number of visits) = 1-probability(y=0) in the last 30 days. Using
poisson distribution for counts, we know that p(y=0)=1-exp(-lamda), we may
then derive lamda value which is the mean of number of visits. How do you
think about this? Thanks very much. Chunling
-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of David Greenberg
Sent: Thursday, May 24, 2007 7:17 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: A question on using survival model
You can't, unless you are confident that those who visited a doctor within
the last 30 days did so only once. David Greenberg, Sociology Department,
New York University
----- Original Message -----
From: Chunling Lu <chunling_lu@harvard.edu>
Date: Thursday, May 24, 2007 12:26 pm
Subject: st: A question on using survival model
To: statalist@hsphsun2.harvard.edu
> Dear all,
>
> I have a question "When was the last time you visited doctor" with the
> following categories: (1) in the last 30 days, (2) between 1 month and
> less than 1 year ago. I now would like to derived the average number
> of visits for last 30 days. How should I model it and how can I do it
> in stata?
>
> Any suggestions are highly appreciated.
>
> Chunling
>
>
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