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RE: st: RE: regression with categorical predictors


From   amir gahremanpour <gamirali@hotmail.com>
To   statalist <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: regression with categorical predictors
Date   Tue, 30 Aug 2011 12:01:48 -0500

thank you, al Feiveson !



----------------------------------------
> From: alan.h.feiveson@nasa.gov
> To: statalist@hsphsun2.harvard.edu
> Date: Tue, 30 Aug 2011 11:57:22 -0500
> Subject: st: RE: regression with categorical predictors
>
> Amir - You are correct. There is no automatic adjustment.
>
> al Feiveson
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of amir gahremanpour
> Sent: Tuesday, August 30, 2011 11:07 AM
> To: statalist
> Subject: st: regression with categorical predictors
>
> Hello everybody,
>
> First let me apologize if my question is very primitive, I am trying to self educate myself about regression with stata.
> When I have a categorical predictor with more than two levels , I am not sure if the p-values stata provides are adjusted for multiple comparison or are not? This example is from stata documentation , variable region has 4 levels , are the p-values adjusted for 3 comparisons to the base level? I do not think so !
>
> thanks a lot
>
>
>
>
>
>
>
>
>  use http://www.stata-press.com/data/r12/census9
> (1980 Census data by state)
>
> . regress drate medage i.region [w=pop]
> (analytic weights assumed)
> (sum of wgt is   2.2591e+08)
>
>       Source |       SS       df       MS              Number of obs =      50
> -------------+------------------------------           F(  4,    45) =   37.21
>        Model |   4096.6093     4  1024.15232           Prob > F      =  0.0000
>     Residual |  1238.40987    45  27.5202192           R-squared     =  0.7679
> -------------+------------------------------           Adj R-squared =  0.7472
>        Total |  5335.01916    49  108.877942           Root MSE      =   5.246
>
> ------------------------------------------------------------------------------
>        drate |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
> -------------+----------------------------------------------------------------
>       medage |   4.283183   .5393329     7.94   0.000     3.196911    5.369455
>              |
>       region |
>           2  |   .3138738   2.456431     0.13   0.899    -4.633632     5.26138
>           3  |  -1.438452   2.320244    -0.62   0.538    -6.111663    3.234758
>           4  |  -10.90629   2.681349    -4.07   0.000    -16.30681   -5.505777
>              |
>        _cons |  -39.14727   17.23613    -2.27   0.028    -73.86262   -4.431915
> ------------------------------------------------------------------------------
>
> . * testing the joint significance of joint variable
>
>
>
>
>
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