Date:         Wed, 28 Sep 2005 10:36:26 -0300
Reply-To:     Hector Maletta <hmaletta@fibertel.com.ar>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Hector Maletta <hmaletta@fibertel.com.ar>
Subject:      Re: Interpretation of logistic regression ' results
Comments: To: kende jan <kendejan@yahoo.fr>
In-Reply-To:  <20050928132523.62270.qmail@web25410.mail.ukl.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"

The coefficients of dummies measure the significance of the difference
between one category and the reference category. In your case, the reference
category seems to be "in the middle", since two of the other categories have
a negative coefficient and one category (represented by the DIAG(3) dummy)
has a positive coefficient. I suspect that if you use the category
represented by DIAG(3) as your reference category, the other two shown in
the table would show a more significant (i.e. lower) probability, because
they have a larger difference with that category than they have with your
current reference category.
However, I think what is more important is the coefficients of the
categories, and not so much the overall effect of the categorical variable
as such. If DIAG alludes to diagnostic, I suppose it is more important what
the diagnostic is (i.e. which category), than the fact that some diagnostic
existed.

Hector

> -----Original Message-----
> From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU]
> On Behalf Of kende jan
> Sent: Wednesday, September 28, 2005 10:25 AM
> To: SPSSX-L@LISTSERV.UGA.EDU
> Subject: Interpretation of logistic regression ' results
>
> Dear all,
>
> In the multiple logistic regression, I have a categorical
> variable (DIAG) with 4 levels, the coefficient on DIAG
> variable is significant but the coefficients of the 3
> indicator variables are not significant.
>
> What can I say about the effect of this variable?
> I cannot make any comparison between levels of this variable.
>
> Thank you for your help
> Jan
>
>
>
> Variable              B      S.E.     Wald    df      Sig
>
>
>
> DIAG                                9.8081     3    .0203
>
>  DIAG(1)        -2.1623    1.4277   2.2939     1    .1299
>
>  DIAG(2)        -1.6487    1.0733   2.3596     1    .1245
>
>  DIAG(3)         1.4109     .9693   2.1185     1    .1455
>
>
>
>
>
>
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