Economic Aspects of Evaluation - Evaluation Methods in Biomedical Informatics - page 329

FIGURE 11.8. Box method for evaluating the confidence limits of a CE ratio. This
figure assumes that the net difference in effectiveness is known for sure, but that
the net change in costs is known with uncertainty, indicated by the upper and lower
limits on the change in costs (DC u , DC L ). Since the slope of the line from the origin
to the intersection of the incremental costs and benefits represents the CE ratio, the
two lines shown indicate the upper and lower bound of the ratio in this case.
FIGURE 11.9. Box method for confidence in CE ratios when both parameters contain
uncertainty. This figure is identical to Figure 11.8 except it is assumed that there is
uncertainty in both the net benefit and the net costs, and each has a range of pos-
sibilities. As you can see, the possible range of CE ratios increases when there is
unknown variability in both parameters.