IBM® SPSS® Amos™ 28

There are two ways to use the AStructure method to specify linear relationships among variables. The first way uses the symbol '<' or the symbol '>' to represent a linear dependency. For example, the following lines specify that variable1 depends directly on variable2.

    Dim Sem as New AmosEngine
    . . .
    Sem.AStructure("variable1 < variable2")

The following lines have the same effect.

    Dim Sem as New AmosEngine
    . . .
    Sem.AStructure("variable2 > variable1")

That is, in the path diagram there is an arrow pointing from variable2 to variable1. Amos estimates the corresponding regression weight.

The AStructure method ignores dashes, so that the following four lines are equivalent.

    Sem.AStructure("variable1<variable2")
    Sem.AStructure("variable1 <--- variable2")
    Sem.AStructure("variable1 <---------- variable2")
    Sem.AStructure("variable2 ----------> variable1")

By default, Amos assumes that the regression weights are unconstrained. However, you can set the value of any regression weight to a constant, and you can require any number of regression weights to be equal to each other. The following example shows how to impose such constraints:

    Dim Sem as New AmosEngine
    . . .
    Sem.AStructure("variable1 <--- variable2 (red)")
    Sem.AStructure("variable1 <--- variable3 (red)")
    Sem.AStructure("variable1 <--- variable4 (1)")
    Sem.AStructure("variable1 <--- variable5")
    Sem.AStructure("variable1 <--- variable6 (blue)")
    Sem.AStructure("variable1 <--- variable7 (blue)")
    Sem.AStructure("variable1 <--- variable8 (blue)")
    . . .

In this example, the first two regression weights are required to be equal because they are both labeled red. Similarly, the last three regression weights are required to be equal because they are both labeled blue. The regression weight for the regression of variable1 on variable4 is fixed at 1. (Amos will not attempt to estimate this regression weight.) The regression weight for predicting variable1 from variable5 is not constrained.