382
Example 25
There are many chi-square statistics in this table, but only two of them matter. The
Sörbom procedure comes down to two basic questions. First, does the Structural
weights model fit? This model specifies that the regression weight for predicting
post_verbal from pre_verbal be constant across groups.
If the Structural weights model is accepted, one follows up by asking whether the
next model up the hierarchy, the Structural intercepts model, fits significantly worse.
On the other hand, if the Structural weights model has to be rejected, one never gets to
the question about the Structural intercepts model. Unfortunately, that is the case here.
The Structural weights model, with and , is rejected at any
conventional significance level.
Examining the Modification Indices
To see if it is possible to improve the fit of the Structural weights model:
EClose the output viewer.
EFrom the Amos Graphics menus, choose View > Analysis Properties.
EClick the Output tab and select the Modification Indices check box.
EClose the Analysis Properties dialog box.
EFrom the menus, choose Analyze > Calculate Estimates to fit all models.
Only the modification indices for the Structural weights model need to be examined
because this is the only model whose fit is essential to the analysis.
EFrom the menus, choose View > Text Output, select Modification Indices in the navigation
tree of the output viewer, then select Structural weights in the lower left panel.
EExpand the Modification Indices node and select Covariances.
As you can see in the following covariance table for the control group, only one
modification index exceeds the default threshold of 4:
M.I. Par Change
eps2 <--> eps4 4.553 2.073
χ236.34=
df 7=