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Extensions
There are several ways to extend the ordered regression models considered thus far in
order to account for more complex patterns and data structures. For example, researchers
may have hypotheses that require the use of interaction terms, which is more complicated
in categorical models such as ordered regression (Williams 2009; Mood 2010). The non-
linear nature of the probability model can cause problems due to potential differences in
unobserved heterogeneity among groups or levels of a variable included in the interaction
term. One may address this problem by explicitly modeling the residual variance and
the categorical outcom ...