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322 Decisions involving groups of individuals
Median True
answer
Product sales
(a)
Median True
answer
Product sales
Figure 12.2 – The accuracy of the median estimate
(b)
Many variations on the theme of Delphi have been tried, including
individuals weighting their own expertise to indicate how much they
thought that their judgments should contribute to the final tally. Indeed,
many procedures for assessing opinions in an anonymous way and then
feeding these back to the panel of participants as a basis for reassessment
have been termed Delphi. 15
However, experimental tests of these techniques as ways of improving
judgmental accuracy have produced mixed results. They improve
performance over the simple average of the individual judgments only
slightly and seldom do as well as the best member of the group. Ferrell 16
has argued that the reason for the poor performance of the methods
is due to the fact that information sharing is small. This is because
participants are anonymous and only a simple statistical summary of
others’ judgments is fed back. It follows that the technique does not help
the individual to construct an alternative theory or scenario with which to
produce a revised prediction. Ferrell argues that one may be encouraged
to change one’s opinion if one’s prediction is away from the rest of the
group (and one has some uncertainty about the truth of one’s answer)
and be encouraged to hold tight if one is close to the rest of the group.