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Specification Search
Madigan and Raftery (1994) suggest that only models in Occam’s window be used
for purposes of model averaging (a topic not discussed here). The symmetric Occam’s
window is the subset of models obtained by excluding models that are much less
probable (Madigan and Raftery suggest something like 20 times less probable) than the
most probable model. In this example, the symmetric Occam’s window contains
models 7, 6, and 8 because these are the models whose probabilities (BICp values) are
greater than .
Rescaling the Bayes Factors
EOn the Current results tab of the Options dialog box, select Akaike weights / Bayes factors
(max = 1) in the BCC, AIC, BIC group.
In the table of fit measures, the column that was labeled BICp is now labeled BICL and
contains Bayes factors scaled so that the largest value is 1. This makes it easier to pick
out Occam’s window. It consists of models whose BICL values are greater than
; in other words, Models 7, 6, and 8. The L subscript on BICL is a
reminder that the analogous statistic BCCL can be interpreted as a likelihood.
0.860 20⁄0.043=
120⁄0.05=