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Re: st:Transformation for skewed variables with negative values?


From   "woong-tae chung" <Woong.Chung@colorado.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st:Transformation for skewed variables with negative values?
Date   Sun, 15 Aug 2004 11:20:39 -0600

thanks for your suggestion. 
WT 
----- Original Message ----- 
From: "Jeph Herrin" <junk@spandrel.net>
To: <statalist@hsphsun2.harvard.edu>
Sent: Tuesday, August 15, 2006 9:38 AM
Subject: Re: st:Transformation for skewed variables with negative values?


> If your variables are hopelessly non-normal, you should consider converting
> them to categorical or dichotomous variables.
> 
> Otherwise, you can transform your variables by changing the sign to reverse
> the direction of skewness and substracting (mininum-1) to make them
> strictly positive. Thus, if Y has negative skewness, -Y has positive skewness;
> and if X takes negative values, X-(min(X)-1) will be strictly positive.
> 
> hth,
> Jeph
> 
> 
> 
> 
> Woong.Chung@colorado.edu wrote:
> > Hello.
> > I need following help. I have panel dataset for estimating a simple linear
> > equation.
> > The problem is that my all variables have sknewness and big variation(large
> > std).
> > In particualr, the dependent variable and one of independant variables have a
> > negative sknewness, while all other independant variables are shown by positive
> > sknewness. My first intension is using a log transformation of all variables but
> > seems not to be a good idea since all variables have negative values (around
> > 20%)
> > Besides, all variables except one of independant variables are ratio, thus that
> > idea would make worse.
> > 
> > I would be so glad if anyone has suggestions to solve this problem
> > 
> > THANKS
> > 
> > WT
> > 
> > *
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