CTQ trees (critical-to-quality trees) are the key measurable characteristics of a product or process whose performance standards or specification limits must be met in order to satisfy the customer.
CTQs are used to decompose broad customer requirements into more easily quantified elements.
CTQ trees are often used as part of Six Sigma methodology to help prioritize such requirements.
Customers may be surveyed to elicit quality, service and performance data.
The CTQ practitioner converts them to measurable terms using tools such as DFMEA.