Quality Function Deployment (QFD) and House of Quality (HOQ)

House of Quality

Quality Function Deployment is a planning process for products and services that starts with the voice of the customer. Basically, it enables people to think together.

Using QFD allows the charting of customer wants and the technical hows which results in a better understanding of design relationships. You can also include a competitive analysis. People on your team will be better aligned and able to think together towards a solution.

What is the  House of Quality?

The House of Quality is a voice of customer analysis tool and a key component of the Quality Functional Deployment technique. It starts with the voice of the customer. It is a tool to translate what the customer wants into products or services that meet the customer wants in terms of engineering design values by way of creating a relationship matrix.

  • Typically the first chart used in Quality Function Deployment
  • Data intensive and is capable of capturing large amounts of information.
  • Left side: has the customer’s needs.
  • Ceiling: has the design features and technical requirements.
  • The Roof: a matrix describing the relationship between the design features. Used to show how the design requirements interact with each other.
  • Competitive Section: based primarily on the customer’s perspective.
  • Lower level / Foundation: Benchmarking & target values used to rank the ‘hows’. These are the actions your organization will take to satisfy your customers.

House of Quality

OK, this isn’t the best example of CTQs. They should be written from the perspective of the end user. Better ones would be:

  • Website is easy to find.
  • Website has great, fresh content
  • I would buy from this website


Quality Function Deployment functions such as house of quality are used on consumer products to identify and manage design trade-offs. It involves studying customer requirements. The customer requirements can be in the form of a marketing survey which has been targeted towards a certain marketing group. It may not work well for existing products but the results are quite efficient if you are looking into solving a big design problem. Normally, the purpose of this survey is to find out what the consumers want from the consumers. The house of quality serves as a good patch between the customer requirements and the engineering variables.

Let us help you understand it with an example:

  1. We pick a car on which we are going to perform a house of quality analysis. The first things you need to decide are the customer requirements. Since this is a hypothetical scenario we are going to assume all the data. The six min requirements from a car may be: Speed, Safety, Low Fuel Consumption, reliable and cheap. The design requirements may be conflicting too sometimes, which is a good thing. It will help broaden you take on this subject if the requirements are conflicting.
  2. The next thing we do is assume the importance of each of these characteristics of the car. Like what is important according to the customers. What is vital for their car and what is something that is not much important to them. Rate each of the factors on any type of scale you want to. For example let us rate all of these on a scale of 1 to 5 with 5 being the most important and 1 being the least. We rate Speed with a 3, Safety with a 4, Low Fuel Consumption with a 3, reliable with a 3.5 and cheap with a 5.
  3. Now the next thing to do is calculate a percentage of the importance of each factor relative to the rest. This percentage may be calculated by adding all the ratings and dividing the individual rating of each of the factors with this total to calculate the individual percentage.
  4. The next thing you need to do is figure out the engineering parameters that you need in order to design the car. These may include e.g. weight, type of engine (power), Cost of production, expected lifetime, Dimensions and acceleration speed etc. This step can be quite difficult as it involves people working in groups to skim out the variable that may affect the customer requirement factors the most. It is also a very good way to help establish the importance.
  5. Then move to the top of the house. The first row is called up or down. In this column you describe whether a following parameter is better with a high value or low. For example it is always better we have low weight, high engine power and life, low cost of productions, high dimensions and acceleration.
  6. You then use symbols to describe the relationships between the engineering parameters. For example how will the weight affect the cost of production? Well if you plan to use smarter materials the cost of production may increase with the decrease in weight. Similarly you are now to compare the effects of changing one alternative on the others. You can use symbols such as ++ to represent strongly positive effect, + for a positive effect, 0 for no effect, – for negative and – for strongly negative effect.
  7. Now fill in all the boxes of the design parameter columns. This is the biggest and most difficult part of the design process. The first thing you need to do is decide upon a scale. Decide the symbols that you want to use to describe the grades you want. These should be consistent and easy to understand. Fill these columns on the basis of interrelations. E.g. rate how the weight is related to speed, fuel consumption, safety, size, reliability and price. Do this for all the alternatives.
  8. Now all the associations that you have written have a numerical percentage value which you can find by multiplying them with the percentage calculated in part 3.
  9. Sum up all of the percentages for each column of the engineering parameters and write the sum at the bottom of the table. This is the total importance of each individual engineering parameter. The only other thing left to do is to calculate the normalized percentage of importance using these values. You add them up and then divide each individual importance value with the total to get the percentages. This will help you decide which parameters you need to focus on in order to meet the public’s demands. It will also shed some light on the relative importance of each parameter in the design process.
  10. You can use as many designs as you want and can take up as many alternatives as you want. It is all up to you! It all depends on the data you have available, the amount of detail you want to go to and the extent to which you are willing to invest your time and resources for this process. This is a very time taking process if done manually as there are a lot of decisions to be made. You have to decide which factors are worth considering and which are not for one.
  11. You can also use further add-ons to compare different alternatives to check how the different types of cars shape up with all the other alternatives. You can use these add –on to check new designs that you make and learn to select the best optimization for anything you want to make. This also helps identify discrepancies that you may have in your designs – know what you are lacking in your design that the public requires. This is a good way to get everything in there at once. It is also suggested that you sign it as soon as you agree on something.


Six Sigma Black Belt Certification QFD Questions:

Question: Which of the following tools is used extensively in quality function deployment (QFD)?

(A) Affinity diagram
(B) Matrix diagram
(C) Cause and effect diagram
(D) Activity network diagram

Answer: (B) Looking at the ‘house of quality’ diagram above you can see the matrix diagram in action. The affinity diagram is used in brainstorming to group like terms together. The cause and effect diagram helps with root cause analysis and looks like a fish bone. The activity network diagram helps show your project timeline.

3 comments… add one
  • abhay

    How we can draw roof matrix. please give detail about roof matrix.

  • benjamin ndaluka

    what are the relationships between house of quality and quality function deployment

    • Good question. The House of Quality is sometimes referred to as a Quality Function Deployment Matrix. The House of Quality is the first chart used in Quality Function Deployment to design an improvement for a product or a service.

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