After the exchange below, Jennifer asked:
Are you referring to the OR and P-value that is given after the ptl after the second logistic?
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Yes, that's it. In the second command, -ptl- is handled as a continuous variable; it has the actual values 1, 2, 3, 4. Of course, the validity of the trend test depends on the shape of the association between -ptl- and -low- -- as is the case for any trend test.
Svend
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Jennifer wrote:
I am trying to calculate the ptrend for an adjusted OR.
I know that the command ptrend or ptrendi works for my
crude OR, but is there a way to include the other
variables that I am adjusting with.
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Try this:
webuse lbw.dta, clear
xi: logistic low i.ptl i.race i.smoke
xi: logistic low ptl i.race i.smoke
The first -logistic- command displays the 4-category
-ptl- as 3 dummy variables. In the second you get a
single OR, and it can be interpreted as a trend test,
adjusted for race and smoke.
Svend
________________________________________________________
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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