| Date: | Mon, 18 May 1998 13:24:56 -0400 |
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| Reply-To: | Larry W Hawk <lhawk@ACSU.BUFFALO.EDU> |
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| Sender: | "SPSSX(r) Discussion" <SPSSX-L@UGA.CC.UGA.EDU> |
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| From: | Larry W Hawk <lhawk@ACSU.BUFFALO.EDU> |
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| Subject: | Unadjusted means and adjusted means are reversed in MANCOVA |
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| Content-Type: | TEXT/PLAIN; charset=US-ASCII |
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A colleague just asked about a problem with a data analysis. I'm not sure
on all the details, but here's the crux of it.
2 group x 2 time design, with a third level of time as the covariate. (Not
sure if multiple dependent variables are in the model)
Problem is that the covariate-adjusted means for the crossed interaction
are in the opposite direction of the unadjusted means.
I suggested that she check whether the ANCOVA assumptions were met, namely
the assumption that the relationship between the DV and the covariate was
consistent (i.e, does not interact with) any other factor in the design.
My suggestion seemed less than satisfactory (to me). Other ideas...
Thanks,
Larry Hawk
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/ Larry Hawk, Ph.D. / /
/ Assistant Professor / Phone: 716-645-3650 x231 /
/ Department of Psychology / Fax: 716-645-3801 /
/ Park Hall / E-mail: LHAWK@ACSU.BUFFALO.EDU /
/ SUNY-Buffalo / /
/ Buffalo, NY 14260-4110 / /
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