Critical to Quality Tree (CTQ)

Critical to quality tree
Critical to quality tree

Critical to quality tree


A Critical to Quality Tree (CTQ Tree) reflects what the consumers of your process cite as absolutely essential to success. This helps clarify what is considered a defect in the process. It also helps to distinguish what your client’s needs vs what their requirements are.

Use a CTQ tree when you want to investigate your customer base by moving from general needs to more specific ones.

CTQ Tree Steps

  1. Identify who your clients are.
  2. Solicit Voice of Client.
  3. Translate that data into Critical to Client measures. Set ranges and tolerances for the CTCs.
  4. Determine how well your organization’s process needs to do internally in order to meet those measures.
  5. Set parameters for your internal processes that  deliver to those measures- those are your Critical to Quality measures CTQs.

In the measure phase you can use the CTQ tree to distill the outputs that were brainstormed while making a Process Map when creating the data collection plan.

ASQ Green Belt Critical to Quality Questions

Question: Which of the following tools is used to translate broad requirements into specific requirements?

(A) A quality control plan
(B) The theory of constraints (TOC)
(C) A critical to quality (CTQ) tree
(D) A process flowchart

Answer: A critical to quality tree. This is a definition question. A critical to quality tree takes the voice of the client and translates it into what your organization specifically has to do in order to meet those needs.

A process flowchart maps a process. A quality control plan is a way to mitigate defects, ensure good quality, and avoid the costs incurred by poor quality. The theory of constraints states that your process is limited by its weakest link.

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