Hello -
In our section we frequently run multivariate models (usually simply
regressions), and then wish to calculate adjusted values. The model is often
something like:
lung function = age sex infection center_2 center_3 center_4
To calculate the adjusted value for each center we substitute the mean for age,
sex, infection, then simply sum:
adjusted lung function for center_1= intercept + b1*(mean_age) + b2*(mean sex)
+ b3*(mean infection)
adjusted lung function for center_2= intercept + b1*(mean_age) + b2*(mean sex)
+ b3*(mean infection) + b4
adjusted lung function for center_3= intercept + b1*(mean_age) + b2*(mean sex)
+ b3*(mean infection) + b5
adjusted lung function for center_4= intercept + b1*(mean_age) + b2*(mean sex)
+ b3*(mean infection) + b6
where the centers are coded as 0,1 indicators, center 1 is left out as the
referent. The idea is that each center is dealing with the same "average" set
of patients, and the center effect is captured by its coefficient.
First, does anyone else do things this way? Do you have a reference? I have
spent some time on line and in my stats books and can't come up with anything
useful.
Thanks,
Hebe Quinton
Dartmouth Hitchcock Medical Center
Clinical Research/Department of Medicine
506 Rubin
One Medical Center Drive
Lebanon, NH 03756
(603) 653-3536
Fax (603) 653-3554
I am Xena, Worrier Princess.
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