The purpose of Critical To Quality trees is to convert customer needs or wants to measurable requirements for the business to implement. This approach assumes that the customer can articulate what they want. There are, of course, needs and wants, that are unarticulated; for that, ethnography or genchi genbutsu are good approaches.
Critical to Quality Example
A retail merchant was receiving a significant number of complaints regarding their homeowner warranty policies from their customers. By analyzing customer survey data and developing the CTQ tree, the business was able to identify critical-to-satisfaction requirements. These requirements became the focus for improving customer satisfaction.
The business eliminated mandatory warranty visits and made all warranty visits optional. Eliminating mandatory visits satisfied the customers who thought there were too many visits and adding an extra optional visit satisfied customers who thought there were too few visits. Expanding the time frame for scheduling warranty visits from two weeks to three months eliminated the inconvenience for customers who had busy schedules and found the time frame difficult to manage.
The business took a general, difficult-to-measure need (to improve homeowner warranty satisfaction) and developed specific, measurable, and actionable requirements to drive improvements in customer satisfaction.
Critical to Quality Tree (CTQ Tree)
A good and easy way to visualize and organize critical-to-quality requirements is using the CTQ Tree, as shown below:
The CTQ Tree above shows the Customer Needs, Drivers of those Customer Needs, and documented as a CTQ. One can have a CTQ Tree for almost any functional area like the following:
- CTQ Tree for Software Development
- CTQ Tree for Healthcare
- CTQ Tree Hospital
And many more.
Customer to Quality metrics are often a requirement in the Define phase of the DMAIC framework in Six Sigma, but is also used to capture product requirements or service requirements in product development.