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Date:         Tue, 28 Oct 2008 06:13:06 -0700
Reply-To:     shiling99@YAHOO.COM
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Shiling Zhang <shiling99@YAHOO.COM>
Subject:      Re: To statisticians: Units,
              standardization and regression modelling
Comments: To:
Content-Type: text/plain; charset=ISO-8859-1

First, centering variables do not change the values of coefs except constant Second, standardized variables may change coefs. All measures will be at standardized level. It has the advantage to compare the sensitivity among independent variables (sort of) in the sense of one standard unit. Third, when a scale changes, then the corresponding coef will be factored by the amount of scale. Selecting the proper scale in your research area will make it easy to understand for everyone else in you area.

All three are not very important in a regression analysis. Your research area may prefer one to the other.


On Oct 27, 4:13 am, "cat.." <> wrote: > Hi there, > > Let's say I want to fit a logistic model Logit P(diabetis) = Age + > Glucose. > > I usually do not ask for standardizing the covariates before entering > them into the model, only centering them, just to make the > interpretation of exp(beta) easier (= OR when the covariate is > incremented by 1 <unit used in the model>). Centering the covariate > impacts the value of the intercept, reducing them will impact the > value of their coefficient in the model. > > But now, I have a doubt: What about the units ? What senses does it > make to add years and mg/dl ? > > Any thought about that ? > > What is your practice in modeling ? Do you always only work with > standardized variables ? > > Thanks to any contributor. > > Catherine.

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