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Drawing up a broadband plan
Searching for best practice?

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 broadband plan.

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



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