Logical Decisions - Classweb

computed measure levels to common units using the measure’s
SUF.
There are two situations where it makes sense to use measure
categories.
In the first situation, you want to define a measure as a weighted
average of several similar measures. For example, the EPA
publishes two different estimates of the fuel economy for cars and
trucks -- city mileage and highway mileage. Instead of defining
two separate fuel economy measures, you might want to define a
single fuel economy measure as the weighted average of the two
EPA figures. You could define the multipliers for the categories
as the fraction of your total driving that occurs in the city vs. on
the highway. The units for the combined measure will still be
miles per gallon.
You should base the most preferred and least preferred levels on
the range for the alternatives on the combined measure.
The second situation where measure categories are useful is when
you want to define a measure as a weighted sum of several submeasures.
A good example is in facility siting studies, where
several different types of land use may be affected depending on
where you locate the facility.
The reservoir siting analysis described on page 10-12 had a
measure to describe the number and type of prehistoric sites that
would be affected at different locations. The prehistoric sites
measure used the following five categories:
! "Residential Bases with Interpretive Value"
! "Residential Bases"
! "Processing Sites"
! "Isolated Rock Art"
! "Prehistoric Isolates"
Each category level for a reservoir alternative was the number of
sites of the category type found at the reservoir location.
The multiplier for each category was based on the relative
importance of affecting sites of that type. The "Residential Bases
With Interpretive Value" category was selected as a "currency"
category. It was assigned a multiplier of 1.0. The multipliers for
the other categories were defined as the fraction of the impact of
one currency site represented by affecting one of the other
Section 9 -- In Depth 9-11