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Measure 4 looks at the mean log-likelihood of all exceedent events beyond
the confidence level plotted on the X axis. We present figures 4u and 4m
only to illustrate the difference in relation to measure 5 which we strongly
recommend as a solid performance measure. While the mean log-likelihood
against confidence level does help in establishing the
degree of exceedence - it fails as a valid comparative measure
between models. This is because the exceedent
events referred to by a specific choice on the X axis do not correspond
to the same set of events for different models.
Differing sets of exceedent events at the same confidence level imply
differing theoretical maximums for the mean log-likelihood of exceedence
- making direct comparison fallacious. (In addition we note that
figure 4m has no expression of mean log-likelihood for model 5 at the
level because both contributing portfolios do not contribute
an exceedent event. This again highlights the problem of passing
legislation based entirely on evaluations at the
level.)