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Re: st: AW: lincom


From   Nikolaos Pandis <npandis@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: AW: lincom
Date   Thu, 18 Jun 2009 07:53:16 -0700 (PDT)

Dear Martin,

Thank you for the posting. I apologize for being unclear and also because I am asking very basic questions. 

I am not sure I understand the purpose of this command after let's say a linear  regression.

Let's say we have:

xi: regress continvar i.catvar with 3 levels

the regression  table will show levels 2 and 3 and compare them with the reference level 1 of the categorical variable. Why would you run the lincom command. I am not sure I understand its purpose. Would you be able to compare level 2 with level 3 with the lincom command?

Regarding the anova post hoc I meant the following:

If I do a one-way ANOVA like below:

oneway continvar catvar, scheffe

I would get the an F-value and p-value which will be telling me whether there is a sig. difference between any of the category levels, whereas the -scheffe- option will do the "post hoc"- pairwise comparisons between the groups 1&2, 1&3 and 2&3 and tell me which groups are actually different.

Are the objectives of the lincom command similar the  scheffe option in the above examples? Do I have it all wrong? 

Thank you very much.

Nikolaos
--- On Thu, 6/18/09, Martin Weiss <martin.weiss1@gmx.de> wrote:

> From: Martin Weiss <martin.weiss1@gmx.de>
> Subject: st: AW: lincom
> To: statalist@hsphsun2.harvard.edu
> Date: Thursday, June 18, 2009, 4:23 PM
> 
> <> 
> 
> What exactly is a "post hoc" test? Apart from that, the
> help file for
> -lincom- does a good job under "Description". What else do
> you want to know
> about the command?
> 
> Note that -lincom- works after any estimation command, so
> the -regress- case
> may not be as special as you think...
> 
> 
> 
> HTH
> Martin
> 
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]
> Im Auftrag von Nikolaos Pandis
> Gesendet: Donnerstag, 18. Juni 2009 14:46
> An: statalist@hsphsun2.harvard.edu
> Betreff: st: lincom
> 
> Hi,
> 
> I would like to ask if you would possibly direct me to a
> site/article ect
> that explains in detail the use and meaning of the -lincom-
> command (after
> -regress-).
> 
> How is this command related (if it is related) with the
> anova post hoc
> tests.
> 
> Thank you very much.
> 
> Nick
> 
> 
>       
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