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Re: st: Q: stir


From   May Boggess <mboggess@stata.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Q: stir
Date   08 Mar 2004 10:57:08 -0600

On Monday, Cristian asked for references for the command -stir-.

As Richard said in his response, -stir- calls -ir-. So, all that -stir-
is really doing for us, is creating a datset that -ir- can work with. In
other words, it creates var_case, var_exposed and _var_time variables,
as follows:

 clear
 webuse page2
 stset

 gen var_case=_d
 gen var_exposed=(group==2)
 gen var_time = _t - _t0
 ir var_cas var_exposed  var_time

 stir group

You may feel like -stir- isn't doing much for you after looking at this
example, but -ir- only wants its variables in certain formats,
for example exposed must be 0/1, and -stir- can take care of
things like changing strings to 0/1, etc.

A good reference for the formulas is Rothman "Modern Epidemiology". 
In the 1986 edition, the relevant page numbers are:
   -incidence rate  164-172
   -attibutable fraction 38-39
   -midp 155

In the version 8 [ST] manual, this is described on page 61-62.
In the version 7, look on page 482-483 in [R] epitab. 

--May

mmb@stata.com


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