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Re: st: Testing equality of odds ratios outside of logistic regression

From   Steve Samuels <>
Subject   Re: st: Testing equality of odds ratios outside of logistic regression
Date   Sun, 9 May 2010 20:16:41 -0400

You can use -logistic- and test the interactions or -cc- with a test
for homogeneity

use, clear
gen tobac20 = tobacco <=2
xi: logistic case i.tobac20*i.alcohol [fw=freq]
testparm _ItobXa*
cc case tobac20 [fw=freq], by(alcohol) bd
On Sun, May 9, 2010 at 7:49 PM, Michael I. Lichter <> wrote:
> I'm assisting on a paper where we examine the relationship between each of
> four dichotomous predictors variables and one dichotomous outcome variable.
> Prediction is our primary objective. The predictors are all measures of more
> or less the same thing, and we want to know whether, *without controlling
> for any of the others*, they predict the outcome equally well. We want to be
> able to say, "If you could only pick one of these variables as a predictor
> of the outcome, it wouldn't make any difference which one you selected."
> For each of the predictors we calculate a odds ratio and a corresponding
> confidence interval. The odds ratios are very similar in magnitude and have
> confidence intervals that overlap almost entirely. We did not do any formal
> tests, not knowing of any offhand, and, because this isn't a central point,
> we didn't think it was very important. When we reported that the odds ratios
> were essentially equal, a reviewer objected that we had not tested for
> equality. Any suggestions?
> In logistic regression, by the way, two of the four variables emerged as
> significant predictors and two did not, controlling for the others. That is
> of interest, but it doesn't answer my initial question. At least, I don't
> think it does.
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Steven Samuels
18 Cantine's Island
Saugerties NY 12477
Voice: 845-246-0774
Fax:    206-202-4783

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