Using GLM or UNIANOVA, (but not REGRESSION) you can directly enter covariate
interactions in the model. Just click the Model button, select Custom, and
build the appropriate interaction term(s).
Using syntax you would add the terms to the /DESIGN paragraph, for example:
y WITH x1 x2
/DESIGN = x1 x2 x1*x2 .
y BY a WITH x
/DESIGN = a x a*x .
y WITH x
/DESIGN = x x*x x*x*x.
As I've hinted in the examples, one can just as easily add a
covariate-by-categorical interaction (for testing homogeneity of slopes), or
perform polynomial regression.
John Bauer, Ph.D.
SPSS Support Statistician
From: Hector E. Maletta [mailto:firstname.lastname@example.org]
Sent: Tuesday, April 20, 1999 2:21 PM
Subject: Re: Interaction terms in regression
just create the interaction variables (e.g. COMPUTE Z= X * W) and then
enter them into the regression. There is no way to create the
interaction terms from inside the regression procedure.
Universidad del Salvador
Buenos Aires, Argentina
David Huffer wrote:
> Is there a way to calculate an interaction term for a regression equation
> SPSS? With SAS you can explicitly define the terms (e.g., model
> y=x1+x2+x3+(x1*x2*x3)), but for whatever reason, SPSS does not allow it
> under "regression". I used GLM and entered the IV's as covariates, which
> should be the same thing -- but still I wonder why I can not enter it
> the regression functions.