The Psychology of Quality and More

A Toolbook for Quality Improvement and Problem Solving (contents)

Tree Diagram: Examples

The Quality Toolbook > Tree Diagram > Examples

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

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Example

A hotel restaurant manager, concerned at low patronage figures and various vague complaints, wanted to find out what affected the satisfaction of her customers in order that areas for improvement might be identified. She decided to use a Tree Diagram to find a basic set of factors to measure that, taken together, would cover all areas. Together with the assistant manager, she defined the method of breaking down the root phrase of 'satisfied customers' as:

• Question to identify children: 'What key factors will directly contribute towards in the parent happening?'.
• Check on children: They should together make up the parent (no key factors missing).
• Break down problem a complete level at a time.
• Stop breaking down when there are about ten leaves on the tree.

The tree generated is shown below. To test the result, a selection of customers were asked to review the diagram, and it was revised accordingly. Measures were then derived from the leaves and a simple process of measurement was set in place. At the end of each month, a project was set up to improve the poorest score of the previous month. Over time, the average score gradually went up, and the restaurant became more popular.

Fig. 1. Example Tree Diagram

Other examples

• An engine design team used a Tree Diagram to record a break-down of the parts of their own and their competitors' engines. Simpler competitive components were clearly identified.
• An improvement work team of metal formers used a Tree Diagram to break down and share out the tasks involved in doing a presentation to managers of a radical idea for workplace layout.
• A teachers' group, having found key types of truancy with a Relations Diagram then moved on to use a Tree Diagram to identify legal remedial measures for each type.

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