Tree Diagram


The tree diagram, called the systematic diagram in the original 7N tools, is a technique to identify the most important, appropriate, and effective means of attaining a given set of objectives. It charts various paths in increasingly unfolding details to achieve a principal objective and other related goals. It deals with details. This type of diagram is used to draw family trees and organization charts. It is based on a logic that Mizuno describes as follows:

When means to achieve a goal are selected, secondary means are necessary to secure primary means; thus the principal means become the goal of the secondary means.[12]

This logic is illustrated in Figure 7.4. It results in various levels of means for a given objective on the logic of what/goal leads to how/means.

Figure 7.4. The Logic of a Tree Diagram


Tree diagrams are among the three most used 7 MP tools, along with affinity diagrams and matrix diagrams. Although the tree diagram can be used as a stand-alone tool, it is much more powerful when used together with other 7 MP tools. When used as part of the MP tool kit, it is deployed after the key issues have been identified following the construction of the affinity diagram and I.D. Tree diagrams have numerous applications. A few typical examples are identifying various tasks to be carried out to achieve an objective, carrying out a cause-and-effect analysis, converting customer desires into product features and characteristics in a QFD application, and identifying the steps needed to implement a project. The typical steps of constructing a tree diagram are as follows:

1.

Assemble the team. It is best to have the same team that constructed the affinity diagram and I.D. If this is an original problem, the team members should have worked successfully as a team in the past and should have firsthand knowledge of the problem or opportunity to be discussed.

2.

Agree on the problem statement. Define the effect, characteristic, or problem as precisely as possible. The statement often comes from the I.D.'s key issue (the one with the most arrows coming from it) or the secondary issue (the one with the most arrows going into it). It is advisable to choose the key issue as the statement as the team gets to the heart of the problem, but sometimes the secondary issue puts the original problem in a whole new light.[13] Other sources of the statement are one of the header notes or the affinity diagram's problem statement. Or it could be a new or stand-alone problem that has not been analyzed before. Write the problem statement on a sticky note and place it on the left side of the flip chart or board. This is the objective or target to be achieved.

3.

Identify the primary means. In case of a new problem, the team members brainstorm the primary means to achieve the objective: "How can we achieve the objective/target?" The team should be focused on the basic objective rather than subsidiary objectives that very often get cited during discussion. There's almost always more than one primary means, and they should all be written on sticky notes and placed to the right of the objective. Draw lines connecting the roots (objective) and branches (primary means). If the problem has been analyzed before, here are the two possibilities:

  • If an affinity diagram was constructed, and one of the header notes was used as the objective of the tree diagram, use the various notes to identify secondary means. Brainstorm further on these notes. If the affinity diagram's problem statement is also the tree diagram's objective, use all the header notes as the first set of brainstorming ideas to identify the primary means.

  • Alternatively, if an I.D. has been constructed and the tree diagram's objective has been chosen from the key or secondary issue, all the notes connecting to the chosen issue make the first pack of brainstorming ideas.

4.

Identify the secondary means. Proceed by asking: "How can we achieve the primary means?" for each of the primary means identified in the earlier brainstorming session. When agreement is reached on various secondary means following brainstorming, write them on sticky notes and place them on the flip chart to the right of the primary means. Do this for each of the primary means, and connect all the primary and secondary means.

5.

Identify the third and higher-order means. Repeat step 4 for the second and higher-order means. Usually this process is carried out to the fourth order when actionable and specific means may be identified.

6.

Check the logic of relationships between objectives and means. You confirm the validity of each objective/means relationship by asking: "Will this means lead effectively to this objective?" This should be done for each order, from right to left. Do it all again in reverse, from left to right: "Will the objective be achieved if we implement these means?" Identify corrective steps by further brainstorming if the answer to any of the questions is "no."

Figure 7.5 shows a simple tree diagram.

Figure 7.5. A Tree Diagram





Design for Trustworthy Software. Tools, Techniques, and Methodology of Developing Robust Software
Design for Trustworthy Software: Tools, Techniques, and Methodology of Developing Robust Software
ISBN: 0131872508
EAN: 2147483647
Year: 2006
Pages: 394

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