This preview shows page 1. Sign up to view the full content.
Unformatted text preview: fficients corresponding to a covariate (such as midline
episiotomy) is allowed to vary by every level of the
ordinal response. The regression coefficient corresponding to the polytomous model for the first logit
comparison (1 ° versus no laceration) is negative
(–0.4661), resulting in a relative risk estimate of 0.6
(95% CI : 0.3–1.3). However, the coefficients for other
logit comparisons are all positive, implying that midline episiotomy increases the likelihood of lacerations
of 2°. Women with midline episiotomy are 5.4 (95%
CI : 3.7–7.9) times at greater risk of a 4° laceration
relative to women with no episiotomy. Notice the monotonic increase in the regression coefficients for
midline episiotomy. The results of fitting an adjacentcategory logit model are somewhat similar to that of the
polytomous model, although the underlying model
assumption differ; the latter model involves comparing
women with 1° to no laceration (first logit), 2° to 1°
(second logit), and so on, while the logit comparisons
for the polytomous model correspond to each category
of laceration versus a ba...
View Full Document
This document was uploaded on 02/25/2014.
- Spring '11