LISTSERV at the University of Georgia
Menubar Imagemap
Home Browse Manage Request Manuals Register
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (May 1997, week 1)Back to main SAS-L pageJoin or leave SAS-L (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Mon, 5 May 1997 16:07:21 +0200
Reply-To:     Hans-Peter Piepho <piepho@WIZ.UNI-KASSEL.DE>
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         Hans-Peter Piepho <piepho@WIZ.UNI-KASSEL.DE>
Subject:      Re: GLM and interaction contrasts
Comments: To: Jason Jones <jasonj@RCF.USC.EDU>
Content-Type: text/plain; charset="us-ascii"

>Does anyone know of a good place to find out about constructing = >interaction contrasts in PROC GLM? I can construct contrasts across = >single factors fine, but not with interactions. I know it's possible, I = >just don't understand how they're constructed. > >For instance, in a 3*3 design, one possible contrast across either = >factor would be -1 1 0. However -1 0 0 0 0 0 0 0 1 is not a valid = >interaction contrast, though that's how many means there are.

The model is overparamaterized. Therefore, contrasts among interactions are not estimable. If you want contrasts among the 9 individual means of the 3 x 3 design, use the cell means model.

model y=a*b; contrast '-11 + 33' -1 0 0 0 0 0 0 0 1;

_______________________________________________________________________ Hans-Peter Piepho Institut f. Nutzpflanzenkunde WWW: http://www.wiz.uni-kassel.de/fts/ Universitaet Kassel Mail: piepho@wiz.uni-kassel.de Steinstrasse 19 Fax: +49 5542 98 1230 37213 Witzenhausen, Germany Phone: +49 5542 98 1248


Back to: Top of message | Previous page | Main SAS-L page