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3
Decisions involving multiple
objectives: SMART
Introduction
As we saw in the last chapter, when decision problems involve a number
of objectives unaided decision makers tend to avoid making trade-offs
between these objectives. This can lead to the selection of options
that perform well on only one objective, or the rejection of relatively
attractive options because their good performance on several objectives
is not allowed to compensate for poor performance elsewhere. A laptop
computer is rejected because of its slow processor speed, despite its
compactness, reliability and low price. A supplier is chosen because
of his low price, despite his slow delivery times and poor after-sales
service. These problems arise because the unaided decision maker has
‘limited information-processing capacity’ (Wright 1 ). When faced with
a large and complex problem, there may be too much information to
handle simultaneously so the decision maker is forced to use simplified
mental strategies, or heuristics, in order to arrive at a choice.
This chapter will explore how decision analysis can be used to support
decision makers who have multiple objectives. As we stated in Chapter 1,
the central idea is that, by splitting the problem into small parts and focusing
on each part separately, the decision maker is likely to acquire a better
understanding of the problem than that which would be achieved by taking
a holistic view. It can also be argued that, by requiring a commitment
of time and effort, analysis encourages the decision maker to think deeply
about the problem, enabling a rationale, which is explicit and defensible,
to be developed. After such analysis the decision maker should be better
able to explain and justify why a particular option is favored.
The methodology outlined in this chapter is underpinned by a set of
axioms. We will discuss these towards the end of the chapter, but, for the
moment, we can regard them as a set of generally accepted propositions
or ‘a formalization of common sense’ (Keeney 2 ). If the decision maker