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Constructing a value tree 31
offices compare when considering the quality of the working
conditions they offer?
Stage 5: Determine a weight for each attribute. This may reflect how important
the attribute is to the decision maker (though we will
discuss the problem of using importance weights later).
Stage 6: For each alternative, take a weighted average of the values assigned
to that alternative. This will give us a measure of how well an
office performs over all the attributes.
Stage 7: Make a provisional decision.
Stage 8: Perform sensitivity analysis to see how robust the decision is to
changes in the figures supplied by the decision maker.
Constructing a value tree
Stages 1 and 2 of our analysis have already been completed: we know
who the decision maker is and we have identified the courses of action
open to him. The next step is to identify the attributes which the decision
maker considers to be relevant to his problem. You will recall that an
attribute is used to measure the performance of courses of action in
relation to the objectives of the decision maker. This means that we need
to arrive at a set of attributes which can be assessed on a numeric scale.
However, the initial attributes elicited from the decision maker may be
vague (e.g. he might say that he is looking for the office which will be
‘the best for his business’), and they may therefore need to be broken
down into more specific attributes before measurement can take place.
A value tree can be useful here, and Figure 3.1 shows a value tree for
this problem.
Costs Benefits
Turnover Working conditions
Rent Electricity Cleaning Closeness Visibility Image Size Comfort Car
to customers
parking
Figure 3.1 – A value tree for the office location problem