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st: RE: RE: test difference of two linear combinations that are differences of means
From
"Radwin, David" <[email protected]>
To
<[email protected]>
Subject
st: RE: RE: test difference of two linear combinations that are differences of means
Date
Fri, 7 Feb 2014 12:39:15 -0500
Mark,
Thank you. That worked great. I appreciate your help.
David
--
David Radwin, Senior Research Associate
Education and Workforce Development
RTI International
2150 Shattuck Ave. Suite 800, Berkeley, CA 94704
Phone: 510-665-8274
www.rti.org/education
> -----Original Message-----
> From: [email protected] [mailto:owner-
> [email protected]] On Behalf Of Schaffer, Mark E
> Sent: Friday, February 07, 2014 2:34 AM
> To: [email protected]
> Subject: st: RE: test difference of two linear combinations that are
> differences of means
>
> David,
>
> > -----Original Message-----
> > From: [email protected] [mailto:owner-
> > [email protected]] On Behalf Of Radwin, David
> > Sent: 06 February 2014 21:03
> > To: [email protected]
> > Subject: st: test difference of two linear combinations that are
> differences of
> > means
> >
> >
> > Dear Statalisters,
> >
> > How do I test whether the difference of two linear combinations is
> statistically
> > significant if the linear combinations are differences of means?
> >
> > In the contrived example below, I want to test whether the 0.08 absolute
> mean
> > difference between the South and West in mean January temperatures is
> > different than the 8.88 absolute mean difference between the South and
> West
> > in July temperatures.
> >
> > I can't use -suest- as some earlier posts have suggested because I get
> the error
> > message, "impossible to retrieve e(b) and e(V) in A" (error 198).
>
> -suest- works after -regress- (among other commands). Can you rejig your
> example so that the means are estimated by -regress- and reported as
> coefficients? E.g., instead of
>
> mean tempjan, over(region)
>
> use
>
> reg tempjan ibn.region, nocons
>
> HTH,
> Mark
>
> >
> > David
> > --
> > David Radwin, Senior Research Associate
> > Education and Workforce Development
> > RTI International
> > 2150 Shattuck Ave. Suite 800, Berkeley, CA 94704
> > Phone: 510-665-8274
> >
> > www.rti.org/education
> >
> > . sysuse citytemp, clear
> > (City Temperature Data)
> >
> > . mean tempjan, over(region)
> >
> > Mean estimation Number of obs = 954
> >
> > NE: region = NE
> > _subpop_2: region = N Cntrl
> > South: region = South
> > West: region = West
> >
> > --------------------------------------------------------------
> > Over | Mean Std. Err. [95% Conf. Interval]
> > -------------+------------------------------------------------
> > tempjan |
> > NE | 27.88537 .2766693 27.34241 28.42832
> > _subpop_2 | 21.69437 .3397395 21.02764 22.36109
> > South | 46.1456 .6568972 44.85647 47.43473
> > West | 46.22539 .7033823 44.84503 47.60575
> > --------------------------------------------------------------
> >
> > . lincom [tempjan]West - [tempjan]South
> >
> > ( 1) - [tempjan]South + [tempjan]West = 0
> >
> > ------------------------------------------------------------------------
> > ------
> > Mean | Coef. Std. Err. t P>|t| [95% Conf.
> > Interval]
> > -------------+----------------------------------------------------------
> > ------
> > (1) | .0797906 .9624243 0.08 0.934 -1.808925
> > 1.968506
> > ------------------------------------------------------------------------
> > ------
> >
> > . mean tempjuly, over(region)
> >
> > Mean estimation Number of obs = 954
> >
> > NE: region = NE
> > _subpop_2: region = N Cntrl
> > South: region = South
> > West: region = West
> >
> > --------------------------------------------------------------
> > Over | Mean Std. Err. [95% Conf. Interval]
> > -------------+------------------------------------------------
> > tempjuly |
> > NE | 73.35 .1843789 72.98816 73.71184
> > _subpop_2 | 73.46725 .1841403 73.10589 73.82862
> > South | 80.9896 .1881789 80.62031 81.35889
> > West | 72.10859 .4051957 71.31342 72.90377
> > --------------------------------------------------------------
> >
> > . lincom [tempjuly]West - [tempjuly]South
> >
> > ( 1) - [tempjuly]South + [tempjuly]West = 0
> >
> > ------------------------------------------------------------------------
> > ------
> > Mean | Coef. Std. Err. t P>|t| [95% Conf.
> > Interval]
> > -------------+----------------------------------------------------------
> > ------
> > (1) | -8.881006 .4467604 -19.88 0.000 -9.757754
> > -8.004258
> > ------------------------------------------------------------------------
> > ------
>
>
>
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