Logical Decisions - Classweb

Converting the Measures to Common Units
Since LDW allows so much flexibility in defining the scales and
units for the measures, you cannot directly combine the measures
into an overall score. For example, there is no direct way to
combine the price of a car with its horsepower. To combine the
measures, we must first convert them to a common scale.
The common scale used in decision analysis is called utility,
which has units called utils (generally pronounced "you-tills").
Utility is a measure of desirability. The idea is that more utility is
preferred to less and that each util represents the same amount of
"increased desirability."
The default utility scale for each measure has a range from zero to
one, with one being the most preferred.
LDW assigns a utility of zero to alternatives having the least preferred
level for a measure. LDW assigns a utility of one to alternatives having
the most preferred level.
Alternatives having intermediate levels for a measure have a
utility between zero and one on the measure's utility scale. LDW
provides five methods for computing the common units for a
measure:
! Single Measure Utility Functions (SUFs),
! The Analytic Hierarchy Process,
! Adjusted AHP,
! AHP SUFs, and
! Direct Entry.
Two of these methods -- SUFs and AHP SUFs -- use a continuous
function to convert levels on a measure's nominal scale (say
horsepower) to utility. The direct entry method associates utilities
directly with labels or alternatives. The other two methods are
based on the "Analytic Hierarchy Process." They define the utility
for the alternatives by having you directly compare their
performance on a measure without defining an explicit scale for
the measure.
The Analytic Hierarchy Process and adjusted AHP methods don't
use explicit measure levels. Thus, they don't allow the distinction
that the decision analysis method usually makes between the
Section 9 -- In Depth 9-13