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Re: st: frequency matching in case-control study

From   "Svend Juul" <[email protected]>
To   <[email protected]>
Subject   Re: st: frequency matching in case-control study
Date   Sun, 2 Apr 2006 17:41:49 +0200

Raoul wrote:

If I would conduct a case-control study and would want to
frequency match cases and controls, what STATA command would
I have to use? Can I simply include a variable that presents
the group id (1=males age 50, 2=males age 60, 3=female age 50 etc.)
and use .logit? Or should I use .clogit? My understanding is that the
command .clogit is used for individual matched case-control data.

There may be a terminology problem here: In my dialect matching
is a matter of design (how to select controls to participate
in the study), and no Stata command can do that for you. Also,
"frequency matching" is a somewhat ambiguous concept; I think that
it most often means a stratified sampling of controls, ensuring
that there is not too much imbalance, e.g. in age and sex
distribution, between cases and controls.

For crudely frequency matched data (many persons, few groups),
a stratified analysis with -cc- or -mhodds-, stratifying by age
and sex, is appropriate. The regression alternative is -logit-,
but the stratified analysis is more illustrative, I think.
For individually matched data, use -mcc- for a stratified
analysis and -clogit- for a regression.

You might benefit from studying chapter 12 and 13 in Juul: An
Introduction to Stata for Health Researchers. Stata Press 2006.

Hope this helps


Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000 Aarhus C,  Denmark
Phone, work:  +45 8942 6090
Phone, home:  +45 8693 7796
Fax:          +45 8613 1580
E-mail:       [email protected]

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