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Heuristics used for decisions involving multiple objectives 19
If you were to employ this strategy then you would prefer A to B and B to
C. This implies that you will prefer A to C, but a direct comparison of A
and C using the strategy reveals that C is preferred. This set of choices is
therefore contradictory. More formally, it violates a fundamental axiom
of decision analysis that is known as transitivity which states that if you
prefer A to B and B to C then you should also prefer A to C. Thus a
strategy, which on the face of it seemed reasonable, is irrational in that it
contains inherent contradictions. 5
Elimination by aspects (EBA) 6
In this heuristic the most important attribute is identified and a cutoff
point is then established. Any alternative falling below this point
is eliminated. The process continues with the second most important
attribute and so on. For example, suppose that you want to buy a car
and have a list of hundreds of cars that are for sale in the local paper.
You could apply EBA to the list as follows:
(1) Price is the most important attribute – eliminate all cars costing more
than $15 000 and any costing less than $6000.
(2) Number of seats is the next most important consideration – eliminate
two-seater sports cars.
(3) Engine size is the third most important attribute – eliminate any of
the remaining cars that have an engine less than 1600cc.
(4) You want a car with a relatively low mileage – eliminate any remaining
cars that have more than 30 000 miles on the clock.
(5) Service history is next in importance – eliminate any car that does
not have a full service history.
By continuing in this way you eventually narrow your list to one car
and this is the one you choose.
Clearly, EBA is easy to apply, involves no complicated numerical computations
and is easy to explain and justify to others. In short, the choice
process is well suited to our limited information processing capacity.
However, the major flaw in EBA is its failure to ensure that the alternatives
retained are, in fact, superior to those which are eliminated. This
arises because the strategy is non-compensatory. In our example, one of the
cars might have been rejected because it was slightly below the 1600cc cutoff
value. Yet its price, service history and mileage were all preferable to
the car you purchased. These strengths would have more than compensated
for this one weakness. The decision maker’s focus is thus on a single
attribute at a time rather than possible trade-offs between attributes.