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Example 1
The (conditional) expected values of the random variables depend linearly on the
values of the fixed variables.
A typical example of a fixed variable would be an experimental treatment, classifying
respondents into a study group and a control group, respectively. It is all right that
treatment is non-normally distributed, as long as the other exogenous variables are
normally distributed for study and control cases alike, and with the same conditional
variance-covariance matrix. Predictor variables in regression analysis (see Example 4)
are often regarded as fixed variables.
Many people are accustomed to the requirements for normality and independent
observations, since these are the usual requirements for many conventional procedures.
However, with Amos, you have to remember that meeting these requirements leads
only to asymptotic conclusions (that is, conclusions that are approximately true for
large samples).
Modeling in VB.NET
It is possible to specify and fit a model by writing a program in VB.NET or in C#. Writing
programs is an alternative to using Amos Graphics to specify a model by drawing its path
diagram. This section shows how to write a VB.NET program to perform the analysis of
Example 1. A later section explains how to do the same thing in C#.
Amos comes with its own built-in editor for VB.NET and C# programs. It is
accessible from the Windows Start menu. To begin Example 1 using the built-in editor:
E From the Windows Start menu, choose All Programs > IBM SPSS Statistics >
IBM SPSS Amos 21 > Program Editor.
E In the Program Editor window, choose File > New VB Program.