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Re: st: FW: population attritutable risk fraction and xi in logistic regression

From   Nick Cox <>
Subject   Re: st: FW: population attritutable risk fraction and xi in logistic regression
Date   Sat, 7 May 2011 16:14:35 +0100

The difficulty you had with -xi:- that "it did not like interactions"
makes no sense; the whole point of -xi:- is to support interactions.
Your specific difficulty can not be addressed if you do not show the

The other difficulty with -aflogit- I cannot advise on, but everyone
is asked to explain where user-written programs they use come from. In
this case

STB-42  sbe21 .  Adjusted pop. attributable fractions from logistic regression
        (help aflogit if installed) . . . . . . . . . . . . . . . . . A. Brady
        3/98    pp.8--12; STB Reprints Vol 7, pp.137--143
        estimation of the attributable fraction (AF) from within a
        logistic regression framework, thus enabling confounders to
        be taken into account, and allows estimation of the summary
        AF for a set of exposures


On Sat, May 7, 2011 at 3:13 PM, Fitzmaurice, Ann E.
<> wrote:

> I would like to calculate the PAFR after logistic regression  with and without interactions of the form-
> Logistic dependent var1 list of variables var1*each of the variables in the list using xi
> Var1 has four groups , and this is where I think the problem may be
> The first problem got was that the use of xi did not like interactions (do not understand why), so I removed the interactions, but using aflogit, this couldn't find  var1
> This is the command I used
> aflogit bir_grp2, cc
> can anyone explain how to get this fraction from the adjusted model , can it be calculated in stata or by hand and if so does anyone have an example that I can follow

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