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Date:         Fri, 23 Sep 2005 23:09:34 -0400
Reply-To:     Lisa Stickney <Lts1@enter.net>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Lisa Stickney <Lts1@enter.net>
Subject:      Re: GLM Repeated with Categorical Covariates
Comments: To: Stephen Salbod <ssalbod@pace.edu>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
              reply-type=original

Hi Stephen,

There may be a problem with your code. If you have any missing data, you've just relegated it to ethnic4 (the drop out category). When you run through your COMPUTEs for ethnic 1 to 3, teh missing data along with all you other cases got a value of 0. Then in the If statement the valid data for that ethnicity got a value of 1 on that pass, but you never correct the missing data. You might want to try this after the COMPUTE statements:

IF MISSING(ethnic) ethnic1 = $SYSMIS. IF MISSING(ethnic) ethnic2 = $SYSMIS. IF MISSING(ethnic) ethnic3 = $SYSMIS. IF MISSING(ethnic) ethnic4 = $SYSMIS.

Good luck.

Lisa

Lisa T. Stickney Ph.D. Student The Fox School of Business and Management Temple University

----- Original Message ----- From: "Stephen Salbod" <ssalbod@pace.edu> Newsgroups: bit.listserv.spssx-l To: <SPSSX-L@LISTSERV.UGA.EDU> Sent: Friday, September 23, 2005 8:14 PM Subject: GLM Repeated with Categorical Covariates

>A Friday question: I want to us ethnicity (4 levels) as a covariate in an > ANCOVA procedure. I think the code is correct, but since I've never worked > with a set, as covariate, I'm a little concerned. The Syntax Guide had > little to say on this issue (see GLM: Repeated Measures, 726-734). > > > > COMPUTE Ethnic1 = 0. > > COMPUTE Ethnic2 = 0. > > COMPUTE Ethnic3 = 0. > > > > DO IF (Ethnic EQ 1). > > - COMPUTE Ethnic1 = 1. > > ELSE IF (Ethnic EQ 2). > > - COMPUTE Ethnic2 = 1. > > ELSE IF (Ethnic EQ 3). > > - COMPUTE Ethnic3 = 1. > > END IF. > > > > GLM > > pretest posttest BY group WITH ethnic1 ethnic2 ethnic3 > > /WSFACTOR = time 2 > > /METHOD = SSTYPE(3) > > /EMMEANS = TABLES(group*time) WITH(ethnic1=MEAN ethnic2=MEAN > ethnic3=MEAN) > > /CRITERIA = ALPHA(.05) > > /WSDESIGN = time > > /DESIGN = ethnic1 ethnic2 ethnic3 group . > > > > Any suggestions will be most welcome. > > > > TIA. > > > > Stephen Salbod, Pace University, NYC >


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