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Unobserved Variables
The structural part of the current model is the same as the one in Example 4. It is only
in the measurement model that this example differs from the one in Example 4.
Identification
With 13 unobserved variables in this model, it is certainly not identified. It will be
necessary to fix the unit of measurement of each unobserved variable by suitable
constraints on the parameters. This can be done by repeating 13 times the trick that was
used for the single unobserved variable in Example 4: Find a single-headed arrow
leading away from each unobserved variable in the path diagram, and fix the
corresponding regression weight to an arbitrary value such as 1. If there is more than
one single-headed arrow leading away from an unobserved variable, any one of them
will do. The path diagram for “Model A” on p. 83 shows one satisfactory choice of
identifiability constraints.
Specifying the Model
Because the path diagram is wider than it is tall, you may want to change the shape of
the drawing area so that it fits the path diagram better. By default, the drawing area in
Amos is taller than it is wide so that it is suitable for printing in portrait mode.
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