Date:         Wed, 28 Jan 2009 06:22:00 -0800
Reply-To:     SR Millis <srmillis@yahoo.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         SR Millis <srmillis@yahoo.com>
Subject:      Re: Discriminant Analysis - Testing Equal Covariances
Comments: To: Peter Erhardt <ptedar@rit.edu>
In-Reply-To:  <5D049C2353715B498CD1E3C3F19AAA7B045EDA63@svits26.main.ad.rit.edu>
Content-Type: text/plain; charset=us-ascii

Peter:

I would encourage you to do logistic regression than than discriminant function analysis.  In, logistic regression you don't need to worry about homogeneity of var/cov matrices or multivariate normality.  In addition, the interpretation of the relative contributions of the covariates/predictor variables is much easier than in DFA. In logistic regression, the exponeniated coefficient is an odds ratio.

Scott R Millis, PhD, MEd, ABPP (CN,CL,RP), CStat
Professor & Director of Research
Dept of Physical Medicine & Rehabilitation
Wayne State University School of Medicine
261 Mack Blvd
Detroit, MI 48201
Email:  smillis@med.wayne.edu
Tel: 313-993-8085
Fax: 313-966-7682


--- On Wed, 1/28/09, Peter Erhardt <ptedar@rit.edu> wrote:

> From: Peter Erhardt <ptedar@rit.edu>
> Subject: Discriminant Analysis - Testing Equal Covariances
> To: SPSSX-L@LISTSERV.UGA.EDU
> Date: Wednesday, January 28, 2009, 8:53 AM
> I am doing discriminant analysis for 2 groups and I
> don't see an option
> to test whether the covariances between groups are equal.
> In other
> words, I don't know if I should be using the linear or
> the quadratic
> discriminant functions.  In SPSS this is the "Use
> Covariance Matrix:
> "Within Groups" or "Separate Groups"
> option.  However, there is not a
> third option to test this equality like there is in SAS.
>
>
>
> Anyone know of a way to do this in SPSS? Either with an
> option under
> discriminant analysis, or a separate test would be fine.
>
>
>
> I get digest mode usually, so I'd appreciate if you
> respond to me
> directly as well as the list.
>
>
>
> Thanks,
>
> Pete
>
>
>
> Peter Erhardt
>
> Data & Research Specialist
>
> Development & Alumni Relations
>
> Rochester Institute of Technology
>
> 116 Lomb Memorial Drive
>
> Rochester, NY 14623
>
> 585-475-5039 || 585-475-7004 (F)
>
> ptedar@rit.edu
>
>
>
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