# Re: st: differences in relative risks

 From "Paul O'Brien" To statalist@hsphsun2.harvard.edu Subject Re: st: differences in relative risks Date Fri, 12 Mar 2004 16:10:49 +0000

Ricardo,

This might help you - free on BMJ website. Gives the calculations for comparing two estimated relative risks.

Douglas G Altman and J Martin Bland
Statistics Notes: Interaction revisited: the difference between two estimates
BMJ, Jan 2003; 326: 219.

Paul

On 12 Mar 2004, at 00:48, Ricardo Ovaldia wrote:

```Thank you Philip. Unfortunately all I have is the RR
and the corresponding SE. I was thinking that some
method out of the Meta-analysis literature could be
used.

--Ricardo.

```
```One way might be to write out two separate models
(eg logistic or
log-binomial, depending on your research design) and
then use -suest- to
test for equality of the coefficients of the
suitably parameterised
exposures.  For example, as a very general case
where both the exposures
and the outcomes are different (and the sense is
rather open to question!)

is the RR for lung cancer among smokers (vs
non-smokers) different from the
RR of heart disease among males (vs females):

glm lung smoker, link(log) fam(binomial) score(s1)
est store A
glm heart sex, link(log) fam(binomial) score(s2)
est store B
suest A B
test [A_lung]smoker = [B_heart]sex

Phil

At 09:56 AM 11/03/2004 -0800, you wrote:
```
```Dear all,

Is there a way in Stata to compare if two relative
risks are equal, or alternatively if the ratio of
```
```two
```
```relative risks (RRR) is equal to one?

Ricardo.

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=====
Ricardo Ovaldia, MS
Statistician
Oklahoma City, OK

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