Date: Tue, 19 Sep 2006 04:50:36 -0700
Reply-To: IK <bigdoctor2004@GMAIL.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: IK <bigdoctor2004@GMAIL.COM>
Subject: Re: difference between regression coefficients in non-nested
Content-Type: text/plain; charset="iso-8859-1"
I want to be able to make statements regarding which variable X1 or x2
is a better predictor of Y. I tried to use both variables in a nested
regression but cos of multicoll. issues I cant.
i forgot to add - my data is market data - returns and earnings and for
the most part most of the underlying assumptions have not been
violated. i used proc reg initially but then when i couldnt compare
the slopes i included a predicted variable for Y in model 1 and used
proc autoreg and did the same for model 2 i.e. a davidson and mackinnon
test. am i out to lunch on all this?
David L Cassell wrote:
> bigdoctor2004@GMAIL.COM wrote:
> >I have some difficulty solving the following problem: I have an
> >independent var (y) and 2 ind. var (x1 and X2). I am running two
> >non-nested regressions and I want to compare the betas from regression
> >1 with X1 and regression 2 with X2. any help on how to do this is
> Let me see if I have this straight.
> You have two models. Model 1 looks like this:
> model y = x1;
> and model 2 looks like this:
> model y = x2;
> Is that right?
> If so, then what you are asking does not make any sense.
> I advise you not to try to compare the slopes. And don't try
> to compare the standardized betas either.
> Why aren't you look at nested models? Then you would be
> able to see the contribution of one variable, over and above
> what the first one does. You don't even need to do this as
> two separate models.
> And what proc are you using? Have you made sure that all
> the underlying assumptions are valid? Where do your data come
> from? These are all relevant quesitons which may alter the
> advice offered.
> David L. Cassell
> mathematical statistician
> Design Pathways
> 3115 NW Norwood Pl.
> Corvallis OR 97330
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