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Model Fitting and Statistical Software
With the exception of the Stereotype logistic model, all
models described above were fit to the data of Table 3
using the SAS system (SAS Institute, Cary, NC). The
proportional odds and continuation ratio models were
fit using the LOGISTIC procedure with the logit
(logistic) and the cloglog (complimentary log-log) link
function specifications, respectively. The polytomous
and adjacent category logistic models were fit using the
CATMOD procedure with the logit and the alogit specifications for link functions, respectively. The LOGIST
procedure of SAS’s supplemental library (version 5.18)
was utilized to fit both the constrained and the unconstrained partial proportional-odds models. Peterson and
Harrell11 describe the SAS code required to fit the
partial proportional odds models. All models were fit
through the procedure of maximum likelihood estimation, while the adjacent category model was fit using
the weighted least squares procedure. Peterson and
Harrell6,12 however, warn against the use of...
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- Spring '11