ROC = NormalROC(logbetas,us,vars,un,varn)
Compute ROC curve given the parameters. Done
analytically for speed.
The trick here is to solve for the values of x
such that log(l(x)) > logbetas. When the variances
are unequal, there can be two distinct regions.
I basically handle this by brute force, since there
are not too many distinct cases.
This routine is not carefully tested and may
xx/xx/xx dhb Wrote it.
10/4/00 dhb Added caveat about bug possibilities, based
in part on disagreement between this routine
and some Monte Carlo simulations.