Tree Diagram: How to understand it

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When to use it | How to understand it | Example | How to do it | Practical variations

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How to understand it

A common difficulty that occurs when investigating a problem is that it may be understood in broad terms, but the specific detail is not clear. For example, when designing an invoice, it may be known that customer and product details are required, but few people could list every item that should be on the form.

The Tree Diagram gives a simple method of breaking down a problem, one layer at time, into its component parts, as Fig.1.

Fig. 1. Tree Diagram

A key characteristic of the Tree Diagram is that it is a hierarchy (as opposed to a network, such as in the Relations Diagram). Each position or node on the tree has one predecessor or parent and one or more successor nodes, or children (this naming probably originates from its use in family trees). There is one initial node (or root), which has no parent, and multiple bottom-level nodes (or leaves) which have no children.

In many uses of the Tree Diagram, each parent is completely described by its children. Thus the diagram can be reviewed 'bottom-up' to check that the root is satisfied by the combination of all bottom-level leaves.

The method used to build the Tree Diagram is logical and systematic, repeating the same process of analysis and breakdown for each node. This may be contrasted with the more creative and fluid approach used in other methods, such as in building the Affinity Diagram.

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