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Re: st: standardizing variables


From   Ron´┐Żn Conroy <[email protected]>
To   [email protected]
Subject   Re: st: standardizing variables
Date   Thu, 13 Jan 2005 10:50:31 +0000

Hema Mistry wrote:

Dear Sirs,

I am conducting a multivariate regression analysis. One of my independent variables is gestation in weeks. What I would like to do is standardize this variable to the most frequent week for the model cohort. Would the command below be the right one to use?

egen stdgest = std (gest)

Regards Hema

Many sources of data which include gestational age have unusual distributions, resulting from things like scheduling of antenatal visits. Standardizing (in the sense of converting to an arbitrary distribution, such as mean zero, SD 1) is not an option in this case.

However, I suspect that you may want to present results for key gestational ages, such as presenting them for every fifth week of gestation, or for, say, 40 weeks. In a case like this, you can use -adjust- to output the results you need. There's a worked example (involving pregnancy, what's more) in a piece I wrote for the Stata Journal a while back

Conroy RM. Choosing an appropriate real-life measure of effect-size: the case of a continuous predictor and a binary outcome. The Stata Journal 2002;2(3):290-295.




--

Ronan M Conroy ([email protected]) Senior Lecturer in Biostatistics Royal College of Surgeons Dublin 2, Ireland +353 1 402 2431 (fax 2764) -------------------- Just say no to drug reps http://www.nofreelunch.org/

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