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Re: st: comparing differences of rate differences


From   Philip Ryan <philip.ryan@adelaide.edu.au>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: comparing differences of rate differences
Date   Wed, 10 Mar 2004 11:11:21 +1030

Depending on whether your "rates" are true incidence densities or cumulative rates (treated as proportions as your current analyses imply) you could use either the -ir- or -cs- commands of the epitab suite (see -help epitab-). The binary exposure variable is the year and the -by()- option would have race as a 0/1 variable as its argument. The test for heterogeneity is a rather non-powerful test of whether the effect of year on admission differs between the races.

Alternatively, model it (using -poisson- or -binreg- depending on your conception of the rate and the metric you wish to use) with a year*race interaction term.

eg for risk differences:

binreg admitted year race year_X_race, rd

The coefficient on the interaction term is of interest.

Phil




At 04:15 PM 9/03/2004 -0800, you wrote:

Dear all,

This is not really a Stata question but I have been
unsuccessful finding a satisfactory answer. Any
assistance will be greatly appreciated.

I have computed hospital admission rates for two
different years (1996, 2002). To compare these rates I
can simply use Stata’s ­prtest- (or ­tabulate- ) to
test whether these rates differ.

Now, if I compute these rates separately for Whites
and Blacks, how can I test if the change in rates from
1996 to 2002 is different for whites than for blacks?

Thank you,
Ricardo.


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

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