QFD house of quality

What QFD does

Quality function deployment (QFD) translates the voice of the customer into the technical language of the organization, so that design and process decisions can be traced back to what customers said they need. It was developed in Japan in the late 1960s and is associated with Yoji Akao. The first and best-known matrix is the house of quality; further matrices can deploy the priorities down to parts, processes and controls.

The rooms of the house

• Customer requirements (the whats), in the customer's words, each with an importance rating gathered from customers.
• Technical characteristics (the hows): measurable features the organization controls, each with a direction of improvement.
• Relationship matrix: how strongly each how affects each what, scored 9 (strong), 3 (medium) or 1 (weak).
• Correlation roof: whether improving one how helps or hurts another.
• Competitive assessment: how customers rate you and competitors on each what.
• Basement: technical importance, targets and, in fuller versions, technical benchmarks.

How to read the result

Absolute technical importance for each how is the sum of customer importance × relationship strength down its column. Relative importance is that figure as a percent of the total. The hows at the top of the ranking are where targets and design effort matter most. An empty row means a customer need nothing in the design addresses; a row with only weak links is a need at risk. An empty column is a characteristic no customer asked for, which is either a missing requirement or wasted effort. A negative correlation in the roof is a trade-off the team must resolve by design rather than by compromise.

Where it fits with VOC and Kano

QFD is only as good as the requirements that go in. Collect them through interviews, surveys, complaints and observation, and use the Kano model to sort them: basic (must-be) needs cause dissatisfaction when missing but earn little credit when met, performance needs scale with how well they are met, and delighters surprise. Customers rarely mention basic needs, so a house built only from what customers said can miss them.

On the CMQ/OE exam

Expect to name the parts of the house, compute a technical importance from a small matrix, and interpret an empty row, an empty column or a negative roof correlation.

Common questions

What is a house of quality?

The first matrix of quality function deployment (QFD). Customer needs (the whats) run down the side with their importance weights, technical characteristics (the hows) run across the top, the body rates how strongly each how serves each what, the roof shows how the hows affect each other, and the basement holds targets and the ranked technical importance.

What do 9, 3 and 1 mean in QFD?

Strong, moderate and weak relationships. Each technical characteristic scores the sum of customer weight × rating down its column. The wide 9-3-1 spread lets a few strong links outrank many weak ones, which is the point.

What is the roof of the house of quality for?

It shows how the technical characteristics interact. A positive correlation means improving one helps another; a negative one is a trade-off, such as lower weight against higher strength, that the design has to resolve rather than ignore.

Where do the customer needs come from?

From voice of the customer work: interviews, complaints, surveys and observation, translated into needs in the customer's words. The CTQ tree organizes them and the Kano model helps set their weights.

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