# Re: st: comparing rates

 From Ricardo Ovaldia To statalist@hsphsun2.harvard.edu Subject Re: st: comparing rates Date Mon, 8 Sep 2003 09:17:36 -0700 (PDT)

```Dear all,

my original post below), so either of two things is
possible: (1) there is not a good answer or (2) my
question was no clear. So let me ask a slightly
different question.

Can I simply take the number of referrals at one
practice and divide by the number of patients seen at
that practice (referral rate for practice 1) and
compare it to the rate of  the other practice without
taking in account that some physicians within practice
may refer more than others? Or, should I compute the
referral rate for each physician, and then combine
these rates within practice by weighting them some
how?  If so how can I do this in Stata? what kind of
weights should I use?

Thank you,
Ricardo.

--- Ricardo Ovaldia <ovaldia@yahoo.com> wrote:
> Dear all,
>
> We are interested in comparing the referral rates
> for
> two physician practices.   The fist group has 20
> physicians and the second group has 22 physicians.
> Each physician saw a variable number of similar
> patients some saw as few as 4 and others as many as
> 43. The physician either referred the patient to a
> specialist or did not.
>
> If I compute the referral rate for each physician
> group and compare them, I concerned because the
> observations are not independent. I suspect that
> some
> doctors are more likely to refer patients than
> other.
> I though that I could use &#33192;logit- to group by
> doctor&#30196; ID:
>
> . clogit referred practice, group(doctorid)
>
> This did not work because the &#26420;ractice-
variable
> does
> not vary within doctor ID, so it is dropped from the
> model (omitted due to no within-group variance).
>
> Any suggestions will be greatly appreciated.
>
> Thank you,
> Ricardo.
>
>
> =====
> Ricardo Ovaldia, MS
> Statistician
> Oklahoma City, OK
>
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```