The decision tree
There are many levels of decisions which apply in
drawing up a broadband plan. A wealth of information
exists from countries which have already taken decisions
on a number of these levels. A decision tree can
assist governments in establishing best practice for their
A decision tree is a decision support
tool which uses a tree-like model of decisions
and their possible outcomes or consequences.
It comprises three types of nodes:
decision nodes (represented by squares)
chance nodes (represented by circles), and
end nodes (represented by triangles).
The squares represent the focus of a
fundamental decision to be made and the
triangles provide the set of options or solutions
which are available to the decisionmaker.
The circles usually sit between the
squares and the triangles and they introduce
a probability (where appropriate) to
further assist the decision-maker.
In applying this concept to the creation of a national
broadband plan, the challenge can be captured by six
levels of decision nodes (see chart). The decision tree
shown does not contain chance nodes, for two reasons.
First, because the subjective probabilities associated
with any chance node will vary from country to country.
Second, while chance weightings could be introduced
based on, say, the number of countries deciding on particular
options, this may not lead to best practice, but
only indicate a herd mentality.
In ascending the tree, there need not be
strict adherence to the numerical sequence
of decision nodes. Many countries have
followed a varying sequence. In general,
however, levels 1 and 2 would be the most
efficient and logical starting sequence, as
well as the lowest risk for a well-informed
national plan. The advantage of using a decision
tree is that, at each level, there is the
experience of several countries to turn to
for formative thinking.
While the end nodes depicted in the
chart represent the nominal range of options
available to a country at the decision
point level, there can in some cases be a combination of
options. At each level there is the experience of at least
several countries to turn to for formative thinking.
Decision tree: The six levels of decision nodes