SC QUALITY GUILDVoice of the customer to CTQ tree
SCQUALITYGUILD.COM/TOOLS/VOC-CTQ-TREE.HTML
From what the customer said, to what they need, to a characteristic you can measure with a target, drawn as a tree and checked for vague CTQs. Switch to a generic tree diagram to break any goal into means and tasks.
ON THE EXAM · CSSYB II.A.1, CQE V.B.2, CSSBB IV.D.2, CQPA II.D.1 · FREE · NOTHING YOU TYPE LEAVES YOUR BROWSER
Q-BotClick for an explanation of this tool.For educational use. This page is a study aid. The method behind it has far more depth and detail than one page and one tool can cover, and what you see here is not everything the method offers or everything this site offers. For full understanding and application, use the governing standards and texts, and seek further education, training or qualified advice. Results depend on the data you enter, so check them before relying on them.
From words to numbers
Customers describe what they want in their own words: "it leaks", "you're always late", "it's hard to fit". The voice of the customer (VOC) is those words, collected from complaints, interviews, surveys, returns and site visits. None of them can be measured as they stand. A CTQ tree converts them, one step at a time:
- Need: what the customer wants, in a few words. "The pump does not leak."
- Driver: what decides whether the need is met. "Seal integrity at installation."
- CTQ: a measurable characteristic, critical to quality, with a target or limit. "Leak rate at 2.5 bar over 30 s: no detectable leak."
A CTQ without a number is still a need. The tool flags CTQs with no numeric target, and CTQs that still use words like "good", "fast" or "reliable".
The Kano model
Noriaki Kano's model sorts needs into three main kinds (the full model also has indifferent and reverse qualities). Basic (must-be) needs are taken for granted: meeting them earns nothing, missing them causes dissatisfaction. Performance needs give more satisfaction the better they are met. Delighters are unexpected, and pleasing when present.
Basic needs are the ones customers rarely mention until something goes wrong, so they are under-represented in surveys. Delighters become basic over time, as customers get used to them.
The generic tree diagram
A CTQ tree is one kind of tree diagram, one of the seven management and planning tools. Choose "Generic tree diagram" at the top to build the general form: a goal on the left, the means of reaching it to the right, finer means after that, and finally tasks that someone can actually do, each with an owner and a date. Moving right answers "how?"; moving left answers "why?". The checks flag branches that stop short of the task level, a means with only one branch under it (ask "how else?"), and tasks with nobody named. The CTQ tree and the generic tree are saved together, so switching between them loses nothing.
On the exam
Voice of the customer is topic II.A.1 of the 2022 CSSYB Body of Knowledge: expect to place a customer statement on the CTQ tree, and to classify a need with the Kano model. Tree diagrams are among the quality management and planning tools in CQE V.B.2, CSSBB IV.D.2 and CQPA II.D.1; expect to pick the tree diagram for a "break this goal down into actions" scenario and to tell it apart from the affinity diagram (which groups ideas) and the interrelationship digraph (which maps cause and effect).