Re: Continuous covariates interpretation in glme

[Frank E Harrell Jr <f.harrell@vanderbilt.edu>]

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