Logical Decisions - Classweb

no intrinsically correct shape for a SUF, the assessment process
must be subjective. There are two commonly used methods for
assessing a SUF -- mid-level splitting and assessments using
probabilities. These approaches have different theoretical
foundations that are mostly of academic interest. If you know the
differences, you will know which technique you will want to use.
If not, use the technique you feel most comfortable with.
SUF Assessment using Mid-Level Splitting. The mid-level
splitting procedure seeks to identify the level that is exactly midway
(half-way) in preference between a low level and a high level
for a measure. The SUF::Assess Value option implements the
mid-level splitting procedure in LDW. Remember from the
discussion on page 9-15 that this mid-preference level could well
be different from the average of the two ends of the range.
You define the mid-preference level by asking the decision maker
questions about changes in the measure. Specifically the midpreference
level (call it L) is where you prefer a change from the
least preferred level (call it L0) to L and a change from L to the
most preferred level (call it L1) equally. In other words, you want
to find the level L that divides the range from L0 to L1 into two
pieces, each representing an equal change in utility.
In more mathematical terms, if U(x) represents the SUF for the
measure, we want to find the point where
U(L) - U(L0) = U(L1) - U(L).
Remember that you should always prefer L to L0 and you should
always prefer L1 to L. However, you still may feel that the change
from L0 to L is more significant or important than the change from
L to L1. You may feel this even though the result of the second
change (L1) is the most preferred level overall.
Assume when asking these questions about one measure that the
levels of all of the other measures remain constant. You should
think of the questions of in terms of simplified hypothetical
alternatives, even if the levels in the questions are similar to those
for the real alternatives.
If the decision maker cannot answer the questions without
knowing a specific level of another measure, there may be a
preferential dependence between the two measures. Modeling
preference dependencies is beyond the current abilities of LDW.
9-16 Section 9 -- In Depth