Date: Thu, 25 Sep 2003 12:00:57 -0400
Reply-To: "G. David Garson" <Garson@social.chass.ncsu.edu>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: "G. David Garson" <Garson@social.chass.ncsu.edu>
Subject: Re: Correlation
In-Reply-To: <5.1.0.14.0.20030925111043.0248ac78@poste.umontreal.ca>
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Pearson's r for a dichotomy and continuous variable is the same as
point-biserial correlation, which is recommended for this purpose, so
in one sense it is true that a dichotomous or dummy variable can be
used "like a continuous variable" in ordinary Pearsonian correlation.
However, when the continuous variable is ordered perfectly from low
to high, then even when the dichotomy is also ordered as perfectly as
possible to match low to high, r will be less than 1.0 and therefore
resulting r's must be interpreted accordingly. Unequal splits in the
dichotomy and curvilinearity in the continuous variable will both
further depress the maximum possible correlation even under perfect
ordering. Moreover, if the dichotomy represents a true underlying
continuum, one would have attenuated correlation.
Date sent: Thu, 25 Sep 2003 11:20:02 -0400
Send reply to: Charles-Édouard Giguère <ce.giguere@umontreal.ca>
From: Charles-Édouard Giguère <ce.giguere@umontreal.ca>
Subject: Re: Correlation
To: SPSSX-L@LISTSERV.UGA.EDU
> If it's a yes/no variable (dummy variable), I think you can use it as if it
> was a
> continuous variable. Otherwise you can consider the non-parametric correlation.
>
> the syntax is :
> nonpar corr var=var1 with var2.
>
> Charles-Édouard.
>
> At 10:58 2003-09-25, Cathy Smith wrote:
> >Dear All,
> >
> >Pardon my simple question. I have to variables. One is categorical [1,0] and
> >the other is continuous. I would like to find the correlation between the
> >two. Were both variables continuos, I would have done it using the Correlate
> >button in SPSS. Since one is categorical, am not sure how to do it. Please
> >help.
> >
> >Cathy Smith.
> >
> >_________________________________________________________________
> >Instant message in style with MSN Messenger 6.0. Download it now FREE!
> >http://msnmessenger-download.com
>
____________________________________
G. David Garson
Editor, Social Science Computer Review
NCSU Box 8102
Department of Political Science and Public Administration
North Carolina State University
Raleigh, NC 27695-8102
For UPS and Express Mail:
G. David Garson
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E-mail: David_Garson@ncsu.edu
__________________________________________________________
G. David Garson Editor, Social Science Computer Review
NCSU Box 8102 Full Professor, Department of Political
Raleigh, NC 27695-8102 Science & Public Administration, NCSU
Express Mail, add: Tel. 919-515-3067
106 Caldwell (PSPA) Fax 919-515-7333 or 7856
Hillsborough St. E-mail: David_Garson@ncsu.edu
