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Unformatted text preview: is based
on the assumption that the dichotomization for the
logistic model is made close to the optimal point. In
reality, dichotomization can be somewhat arbitrary 1331 REGRESSION MODELS FOR ORDINAL RESPONSES which may violate the underlying assumptions of the
model. The arbitrariness is worsened in situations when
a logistic model is fit to a response that has many
A more intuitive choice between the proportional
odds and continuation-ratio models can be based on the
goals of the statistical analysis. Assuming that both
models are valid, if an a priori interest is to estimate the
risk of 4° laceration relative to other groups (none and
1° – 3° combined), then the cumulative logit model is
the obvious model choice. On the contrary, if the analyst is interested in estimating the risk by comparing 4°
laceration to 3°, then the continuation-ratio model is the
preferred model. In general, the choice of a model depends on how the logits are formulated, a priori. The
analyst should, however, be wary of departures from
the underlying model assumptions (proportional odds
and parallel slopes assu...
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This document was uploaded on 02/25/2014.
- Spring '11