Re: st: standardizing variables

[Ron�n Conroy <rconroy@rcsi.ie>]

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 (rconroy@rcsi.ie) 
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/

--------------------------------------------------------------------------------------------------------------------
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom
they are addressed.
If you have received this email in error please notify the
originator of the message. This footer also confirms that this
email message has been scanned for the presence of computer viruses.

Any views expressed in this message are those of the individual
sender, except where the sender specifies and with authority,
states them to be the views of The Royal College Of Surgeons in Ireland.

--------------------------------------------------------------------------------------------------------------------


*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/