Hi:
Maybe I should have mentioned that I am fitting a logistic regression.with
random intercepts to account for the hierarchical structure of my data. I
was thinking that it would be easier to interpret the result as the increase
in odds ratio per one standard deviation shift.
Am I wrong?
Hind
----- Original Message -----
From: "Frank E Harrell Jr" <f.harrell@vanderbilt.edu>
To: "Ali & Hind Lazrak" <alazrak@telus.net>
Cc: "Stella Karuri" <swkaruri@insightful.com>; "Splus listserve"
<s-news@lists.biostat.wustl.edu>
Sent: Wednesday, February 06, 2008 10:46 AM
Subject: Re: [S] Continuous covariates interpretation in glme
Ali & Hind Lazrak wrote:
Hello
You are right, I wanted to transform the continuous covariates for ease
of interpretation. However, by standardize, I meant
x-mean(x)/sqrt(var(x).
For newbies like me :
I have found that scale() does the job.
Thank you Stella.
Hind
That would seem to cloud rather than help the interpretation
Frank Harrell
----- Original Message -----
*From:* Stella Karuri <mailto:swkaruri@insightful.com>
*To:* Splus listserve <mailto:s-news@lists.biostat.wustl.edu>
*Sent:* Wednesday, February 06, 2008 9:46 AM
*Subject:* Re: [S] Continuous covariates interpretation in glme
Splus does not standardize continous variates – by standardizing I
believe you mean centering to improve interpretability, (if x is the
continuous covariate, x*=(x-mean(x))).
When you specify the formula, you can center your covariate i.e.
instead of
glme( y~ x);
have
xst<- x-mean(x); glme(y~xst)
stella
* From: * s-news-owner@lists.biostat.wustl.edu
<mailto:s-news-owner@lists.biostat.wustl.edu>
[mailto:s-news-owner@lists.biostat.wustl.edu] *On Behalf Of *Ali &
Hind Lazrak
*Sent:* Tuesday, February 05, 2008 5:57 PM
*To:* Splus listserve
*Subject:* [S] Continuous covariates interpretation in glme
Dear all,
I ran a generalized mixed effects model to predict a binary outcome
using the 'glme' procedure. This model has two random subject
(persons nested within companies) and 5 fixed effects terms for the
subjects.
Among these 5 fixed effects variables, 2 are continuous.
As I am interpreting the results I have a question pertaining to the
treatment of continuous covariates:
Does Splus standardize automatically continuous covariates?
Thank you kindly for your answer.
Hind
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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