Expands the Capabilities of SPSS and Excel 

Program Dynamic

SPSS does not make it easy to get at simple main effects and interaction contrasts in its GLM program for the analysis of factorial designs.  For both, you must resort to using syntax.  Although the syntax for isolating simple main effects is straightforward, the syntax for generating interaction contrasts is cumbersome.  It requires use of the \LMATRIX line, which is a nightmare to use.

ZumaStat offers a program where you indicate what contrast you want and then it generates the syntax for the \LMATRIX line for you.  You can then copy and paste it into your SPSS syntax.  ZumaStat also provides syntax to isolate the relevant simple main effects in an easy, efficient way.  It all boils down to simple copy and paste.

In the example below, ZumaStat generates the \LMATRIX syntax for a 4X3X2 factorial design with two covariates.  Interest is in testing the interaction contrast between levels 1 and 3 of Factor B with Levels 1 and 2 of Factor C while collapsing across Factor A.  ZumaStat provides extensive instructions on how to communicate what contrast you want, how to generate the core SPSS syntax using point and click, and how to cut and paste the syntax generated by ZumaStat into the SPSS GLM program. 

In this program, the user is shown on the left side of the dialog box the variables that are in the SPSS active data file (see the example below).  Note the 'Sort' and 'Label' buttons below the listbox.  The 'Labels' button is a toggle switch that allows the user to see the labels associated with the variables or to not see the labels.  In this example, the labels are not shown.  The 'Sort' button is a toggle switch that allows the user to sort the variable list by file order or alphabetically by variable name.  The actions produced by these buttons are instantaneous.

The user identifies the factors in the design and the covariates and then uses the special notational system in the Instructions page to tell ZumaStat the contrast of interest.  The output shown below occurs after pressing the 'Create' button.

How it Appears on Your Screen

The Output

The output appears as follows:

As is tradition in SPSS, the covariates are held constant at a value of zero, but this can be changed by the user to accommodate other values.  ZumaStat explains how and why.