Date:         Thu, 17 Jun 1999 11:49:10 -0500
Reply-To:     "Nichols, David" <nichols@SPSS.COM>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@UGA.CC.UGA.EDU>
From:         "Nichols, David" <nichols@SPSS.COM>
Subject:      Re: help with interactions

The two way interaction A*B is nested within the levels of C. From what
you're saying, I'm assuming this is all within subjects or repeated
measures. You would use the MMATRIX subcommand to specify the desired
comparisons among the means. For simplicity, I'll assume that it's a 2x2x2
and you want to look at the A*B effect within each level of C. You'd have
something along the lines of
 
GLM Y1 TO Y8
 /WSFACTORS A 2 B 2 C 2
 /MMATRIX 'A*B WITHIN C(1)' ALL 1 0 -1 0 -1 0 1 0
          'A*B WITHIN C(2)' ALL 0 1 0 -1 0 -1 0 1.
 
This will give results for each individual contrast, as well as an omnibus
multivariate test for the set. If you have multiple degrees of freedom for
the A*B interaction within each level of C, you might have to run multiple
GLM commands, because you can only use one MMATRIX subcommand, and this
wouldn't produce an omnibus test for A*B within C(1) or within C(2)
separately. If you wanted that, you'd have to run GLM twice.
 
Simple main effects or simple, simple main effects (A within the levels of B
or B*C, for example) are more easily handled using EMMEANS COMPARE.
 
David Nichols
Principal Support Statistician and
Manager of Statistical Support
SPSS Inc.
 
> -----Original Message-----
> From: Michael Dennis [SMTP:awkmrd@GTE.NET]
> Sent: Wednesday, June 16, 1999 3:39 PM
> To:   SPSSX-L@UGA.CC.UGA.EDU
> Subject:      help with interactions
>
> Can anybody out there please tell me how to, using GLM Repeated Measures
> on
> SPSS 8.0 for Windows, test for a 2-way interaction (A*B) AS NESTED WITHIN
> a
> 3-way interaction (A*B*C)?
>
> Thanks, Mike Dennis (Purdue University)