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RE: st: lnskew0


From   "Feiveson, Alan H. (JSC-SK311)" <alan.h.feiveson@nasa.gov>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: lnskew0
Date   Wed, 19 Apr 2006 12:35:44 -0500

Following up on this, transforming by lnskew0, although it might make the sample skewness equal to zero, will not produce anything approximating a normal distribution as your variable takes on only 4 values. So your transformed variable (even if the command "works") will give a new variable that takes on 4 weird non-integer values. As an alternative I suggest analyzing this variable by -ologit- or -gologit-

Al Feiveson


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Ronán Conroy
Sent: Wednesday, April 19, 2006 12:25 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: lnskew0

On 19 Aib 2006, at 17:57, Vivien W. Chen wrote:

>
> I've got a question about using lnskew0 to create a variable that 
> transform skewness as zero. For some unknown reason, I can successfuly 
> create for some variables, but some failed. I list the error message 
> as below.
> Please help if
> you know the answer. Thanks!
>
> Vivien
>
>
>
> .tab mmwkdep
>
>  how well
> youcould
> manage
> working
> depression  |      Freq.     Percent        Cum.
> ------------+-----------------------------------
> 	  0	  14,474       70.00	  70.00
>           1 |      4,429       21.42      91.42
>           2 |      1,293       6.25       97.67
>           3 |        481       2.33       100.00
> ------------+-----------------------------------
>       Total |        296      100.00
>
>
> .lnskew0 mmwkdepLG=mmwkdep
> variable z_ not found
> r(111);


Reproducible on Stata/SE 9.2 on OS X. The command works fine on the mpg variable from the auto dataset, so this may be a problem with your very short scale.

Note that trying to eliminate the skew from a variable whose four values seem to represent ordered categories doesn't seem to have an immediate clear justification. What are you trying to accomplish?

=========
Ronán Conroy
rconroy@rcsi.ie
+353 (0) 1 402 2431
+353 (0) 87 799 97 95
www.flickr.com/photos/ronanconroy




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