Date: Fri, 16 Dec 2005 20:03:16 -0800
Reply-To: David L Cassell <davidlcassell@MSN.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: David L Cassell <davidlcassell@MSN.COM>
Subject: Re: Interpreting an intercept
Content-Type: text/plain; format=flowed
>I have been interpreting intercepts in the past without problems, but
>now i'm facing a multiple regression analysis with columns like:
>Intercept/constant B = 5.5
>The numbers show the impact the three top variables have on a dependent
>variable (salary). How am I supposed to interpret the intercept here?
I don't know whether the above accurately reflects what you are doing, or
After all, you say your real results are columns LIKE what you show us. But
take a guess, based on what you showed us.
So you have a dummy variable WOMAN which is 1 for women and 0 otherwise.
You have a dummy variable CAUCASIAN which is 1 for gringos and 0 otherwise.
You have a dummy variable EXPERIENCED which is 1 for k or more years
and 0 otherwise. And you have an intercept. And nothing else. (This seems
like a really over-simplified model, so I hope you are checking your
diagnostics and making sure your real problem has a reasonable model.)
This means that the intercept is not just an intercept. It is the value of
response when WOMAN=CAUCASIAN=EXPERIENCED=0 . So if you have
inexperienced non-white male workers, this is your mean salary estimate for
them, according to your model.
David L. Cassell
3115 NW Norwood Pl.
Corvallis OR 97330
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