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Mixture Regression Modeling
Improving Parameter Estimates
You can improve the parameter estimates (and also improve Amos’s ability to form
clusters) by reducing the number of parameters that need to be estimated. As we have
seen, the slope of the regression line is about the same for the two groups. Also, the
variability about each regression line appears to be about the same for the two groups.
It is possible to incorporate into the mixture modeling analysis the hypothesis that the
slopes and the error variances are the same for the two groups, thereby reducing the
number of distinct parameters to be estimated. To do this:
E On the path diagram, right-click the single-headed arrow that connects dosage and
performance, choose
Object Properties from the pop-up menu, and enter the parameter
name, b, in the Regression weight text box.
E While the Object Properties dialog box is still open, click E1 in the path diagram.
E In the Object Properties dialog box, enter the parameter name, v, in the Variance text
box.