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Multiple-Group Factor Analysis
Removing Constraints
Initially, the factor means are fixed at 0 for both boys and girls. It is not possible to
estimate factor means for both groups. However, Sörbom (1974) showed that, by
fixing the factor means of a single group to constant values and placing suitable
constraints on the regression weights and intercepts in a factor model, it is possible to
obtain meaningful estimates of the factor means for all of the other groups. In the
present example, this means picking one group, say boys, and fixing their factor means
to a constant, say 0, and then removing the constraints on the factor means of the
remaining group, the girls. The constraints on regression weights and intercepts
required by Sörbom’s approach will be generated automatically by Amos.
The boys’ factor means are already fixed at 0. To remove the constraints on the girls'
factor means, do the following:
E In the drawing area of the Amos Graphics window, right-click Spatial and choose
Object Properties from the pop-up menu.
E In the Object Properties dialog box, click the Parameters tab.
E Select the 0 in the Mean box, and press the Delete key.
E With the Object Properties dialog box still open, click Verbal in the drawing area. This
displays the properties for the verbal factor in the Object Properties dialog box.
E In the Mean box on the Parameters tab, select the 0 and press the Delete key.
E Close the Object Properties dialog box.