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

A house of quality (HOQ) involves collecting and analyzing the “voice of the customer,” and it is a key part of the Quality Functional Deployment technique. It is used to define the relationship between customer desires and the product or company’s capabilities.

Step 1: Customer Requirements – “Voice of the Customer”

The first step in a HOQ is to determine the market segments and identify prospective customers. The team collects customer requirements and rates them on a scale of 1 to 5, with 5 being the most important and 1 being the least. Then they calculate the relative importance.

Step 2: Technical measures

Product requirements or technical characteristics are aligned with the voice of the customer. This step can be quite difficult as it involves people working in groups to skim out the variables that may affect the customer requirement factors the most. Parameters should be meaningful, measurable, and global.

Step 3: Roof / Correlation Matrix

The triangular “roof” matrix of the House of Quality is to identify how the design requirements interact with each other. It helps the designers in the next phase of the QFD project. The triangular matrix looks like a house with a roof. The interrelations are rated strong positive as “+ +,” whereas strong negative as “- -“and blank for no interrelation.

Step 4: Relationship Matrix

Develop a correlation between customer requirements (or the voice of the customer) and the design characteristics or technical requirements. Decide the symbols you want to use to describe your desired grades. These should be consistent and easy to understand.

The ranking system use is a set of symbols for strong, medium, and weak relationships. Each of the symbols represents a value of 9 for strong, 3 for medium, and 1 for weak.

Step 5: Importance Rating

The Importance Rating is the result of calculating the total sum of each column when multiplied by the customer importance factor. It helps to determine where to assign the most resources. Then, calculate the percentage of importance.

Step 6: Competitive Evaluation

Competitive Evaluation helps to understand competitor products that fulfill customer requirements. It is a good idea to ask customers how the product or service rates are in relation to the competition. Use surveys, customer meetings, or focus groups/clinics to obtain feedback. Measure the satisfaction on a scale of 1 to 5, where 1 is highly dissatisfied and 5 is highly satisfied.

Identify more specific target values for technical specifications to satisfy the VOC. This section helps appropriate teams within the origination to develop next-level QFD.

Example of House of Quality (HOQ)

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, which can take many forms. For example, a marketing survey that has been targeted towards a certain marketing group is a way to study customer requirements.

It may not work well for existing products, but the results are quite efficient if you consider solving a big design problem. Usually, the purpose of this survey is to find out what the consumers want from the consumers. The House of Quality is a good patch between customer requirements and engineering variables.

Example: We pick a car on which we are going to perform a house of quality analysis. Since this is a hypothetical scenario, we will assume all the data.

Step 1: Customer Requirements-“Voice of the Customer”

The first thing you need to decide on is the customer requirements.

For example, the minimum requirements for a car might be:

• Speed
• Safety
• Low Fuel Consumption
• Reliable
• Cheap

The next thing we do is assume the importance of each of these car characteristics, like what is important according to the customers.

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.

• Speed-3
• Safety – 4
• Low Fuel Consumption- 3 
• Reliable -3
• Cheap-5

Step 2: Technical measures

The next thing you need to do is figure out the engineering parameters that you need in order to design the car.

• Weight
• Type of engine (power)
• Cost of production
• Expected lifetime
• Dimensions
• Acceleration speed 

It is also a good way to help establish the importance.

Step 3: Roof / Correlation Matrix

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The first row is called up or down. In this column, you describe whether the 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 production, high dimensions, and quick acceleration.

Similarly, you can now compare the effects of changing one alternative on the others. You can use symbols such as ++ to represent a strongly positive effect, + for a positive effect, 0 for no effect,– for a negative, and – – for a strongly negative effect.

Step 4: Relationship Matrix

Now fill in all the boxes of the design parameter columns. This is the largest and most difficult part of the design process.

The ranking system use is a set of symbols for strong, medium, and weak relationships. Also, each symbol represents a value of 9 for strong, 3 for medium, and 1 for weak.

E.g., rate how the weight is related to speed, fuel consumption, safety, size, reliability, and price. Do this for all the alternatives.

Step 5: Importance Rating

Sum up all of the values 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.

Then calculate the percentage of importance: You add them up and then divide each importance value by the total to get the percentages. This will help you decide which parameters you need to focus on to meet the demands of the public.

It will also shed some light on the relative importance of each parameter in the design process.

Furthermore, you can use as many designs as you want and test as many alternatives as possible. It is all up to you! It all depends on the available data, the amount of detail you want to go into, and the extent to which you are willing to invest your time and resources in this process.

However, this process is very time-consuming if done manually, as many decisions must be made. Hence, you have to decide which factors are worth considering and which are not for one.

Step 6: Competitive Evaluation

Use further add-ons to compare different alternatives in order to check how the different types of cars shape up with all the other alternatives.

Use a scale of 1 to 5, with 1 being highly dissatisfied and 5 being highly satisfied. For each customer requirement, rank 1 to 5 to the competitors and also for our product (car).

Also, use this 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.

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  Ted Hessing

  I originally created SixSigmaStudyGuide.com to help me prepare for my own Black belt exams. Overtime I've grown the site to help tens of thousands of Six Sigma belt candidates prepare for their Green Belt & Black Belt exams. Go here to learn how to pass your Six Sigma exam the 1st time through!

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