Logical Decisions - Classweb

Each alternative has a raw score (called a level) on each measure.
The levels for the measures completely describe an alternative for
the purposes of ranking. Thus, it is very important for you to
carefully think about how you define the evaluation measures. If
you use inappropriate or poorly thought-out measures your
ranking results may be non-intuitive and hard to justify.
Measures are discussed further on page 9-8.
LDW relies on you to gather the measure levels for the
alternatives. You should try to be consistent in how you evaluate
the different alternatives, so that the same level on a measure
always means the same thing. Careful definitions of your
measure scales can help.
If you gather data about your alternatives from different sources,
you should try to make sure the sources all compute the measure
in the same way. For example, if you're pricing washing
machines from different stores, make sure the prices you're
quoted are really comparable. Do they include sales taxes and
delivery charges? Have the costs of the options you want been
included? Your results will be incorrect if the prices are based on
different assumptions.
The "Analytic Hierarchy Process" provides a method of
evaluating your alternatives without defining their measure levels
at all. In this approach, you directly compare the alternatives’
performance as part of the preference assessment process. No
scale or units are explicitly defined for the measure. This means
that when you are using the AHP approach for a measure, you do
not need to define any levels for your alternatives on that
measure. In fact, LDW will ignore any levels you have defined
for the alternatives.
Because the AHP method does not make use of explicit measure
levels, it makes it hard to distinguish between the objective
measure levels and the more subjective conversion to common
units. In addition, you lose traceability between the level for an
alternative on the measure and the utility (common units)
assigned the alternative on the measure. For these reasons we
recommend that you use the AHP approach infrequently. We feel
you should only use it for measures that are very subjective and
for which you cannot think of a reasonable quantitative or
qualitative scale. The "Analytic Hierarchy Process" method is
discussed on page 7-15.
Section 9 -- In Depth 9-5