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From |
"German Rodriguez" <grodri@princeton.edu> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: comparing rates |

Date |
Mon, 8 Sep 2003 15:38:17 -0400 |

Ricardo, You could try a random-effects logit model with a doctor random effect: xtlogit referred practice, re i(doctorid) This will give you an estimate of the difference between the practices in the usual log-odds scale. It will also allow for intra-doctor correlation, or the fact that some doctors are more likely to refer patients than others. Stata will even give you a measure of intra-doctor correlation (or see my article with Elo in the Stata journal 3(1) 32-46, 2003 for alternatives). The model does assume that the doctor's propensity to refer patients is independent of the practice; you may think of this as both practices drawing doctors from the same pool. But the model allows for a practice effect on top of that, encouraging or discouraging referrals over and above the doctor's own propensity. An alternative is the conditional logit model suggested by Chris Rohlfs clogit referred, group(doctorid) This is akin to a fixed-effects model; it seems perfectly adequate to me, but it doesn't give you an estimate of the practice effect because, as Chris noted, doctors are nested within practices. Cheers, Germán Rodríguez -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Ricardo Ovaldia Sent: Monday, September 08, 2003 12:18 PM To: statalist@hsphsun2.harvard.edu Subject: Re: st: comparing rates Dear all, I have received only one reply to my post (please see 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 膨logit- to group by > doctor痴 ID: > > . clogit referred practice, group(doctorid) > > This did not work because the 朴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 > > __________________________________ > Do you Yahoo!? > Yahoo! SiteBuilder - Free, easy-to-use web site > design software > http://sitebuilder.yahoo.com > * > * For searches and help try: > * > http://www.stata.com/support/faqs/res/findit.html > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**Re: st: comparing rates***From:*Ricardo Ovaldia <ovaldia@yahoo.com>

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