Testing Simple Effects in SPSS

Thanks to Peter Judge and Marcia Caron for this information.

In class, we used the /lmatrix command in SPSS to test the simple effects of a factorial ANOVA with a significant interaction. A simpler alternative is to use the following command syntax:

/EMMEANS = TABLES(atypetx*btypeocd) COMPARE(atypetx).

The variable names in this statement (atypetx and btypeocd) are the ones I gave these factors in the SPSS data sheet that you can download from the "Factorial ANOVA (with interaction)" page. This command statement will cause SPSS to test the simple effects of treatment at each level of the OCD factor. It looks like the TABLES command supplies SPSS the contrast information that we supplied by hand with the /lmatrix command, and that the COMPARE command tells SPSS to compare means across the different levels of the atypetx factor.

Read more about this syntax and about SPSS command syntax in general by clicking the "Command Syntax Reference" item on the SPSS Help menu.

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