This is part three of a four-part look at three Lean tools for product development. Click here to read part one, here to read part two about the customer journey value stream and here to read part three about Kano analysis.

The scope and purpose of Kano analysis is different than the customer journey value stream (CJVS). Yet they both add their own unique value in understanding the customer experience and decoding the wants needs and delights of the customer. In the same way that Kano analysis increases the scope of our understanding of the customer as well as the limitations to design.

The final tool is quality function deployment (QFD). The purpose of QFD is twofold:

  1. Like the Kano model, it can be used to better understand what design characteristics will lead to greater customer satisfaction.
  2. In my estimation more profoundly, it can be used in challenging the status quo of how a product currently delivers value to a customer or end user.

QFD has been around since 1961, though it’s probably one of the most underutilized tools in the Lean toolbox. The aim of QFD goes along with everything we’ve seen so far – letting the customer pull value through the innovation process.

As an added bonus, this tool speeds up the product development process by removing what doesn’t matter to the customer. Just like the Kano analysis, QFD is interested in what the customer says is important. The format of QFD removes the time-consuming activities that don’t add value. One corollary benefit to this is reduced product complexity and design changes. Researchers have noted that Japanese firms that use QFD made fewer design changes than their American competitors, further reducing design and production startup costs.

In addition, QFD adds value for the organization using it by itself. The structure of QFD creates a clear, standardized and concise legacy of documentation. Businesses can use this documentation as a starting point for future iterations of the same product. The teams in charge of new innovations stand on the shoulders of those that have come before, taking the lessons learned of the past and applying them to the future.

The House of Quality

Like the Kano model, QFD has its own diagram. QFD’s diagram is called the house of quality and its purpose is to visualize how the voice of the customer (VOC) affects the design of the product. There are just a few differences that are noteworthy.

Using Figure 1 as a reference, the structure of the house always starts from the left. This is the VOC. Like the front door of a house, the VOC is always entryway and threshold into the house of quality. It’s where we identify the requirements that are critical to quality (CTQ) for the customer. For our carpet cleaning example, these would be descriptions like “easy to maneuver” and “cleans confined spaces.”

Figure 1: The House of Quality
Figure 1: The House of Quality

Directly to the right of these descriptions is the relative importance of each customer requirement, this is a way to simply appreciate that not all of these features share the same level of importance. This information will be used later on when we make decisions related to what parts of the design we try to come up with new approaches for. This is akin to any priority-ranking matrix.

The Second Story

Skipping for a moment the main living space of the house, we’ll move to the second story. These are where the design and performance features are described. The carpet cleaner would have things like “weight,” “sound” and maybe “extra hose attachments.” The point of this section of the house is to identify what performance characteristics and design components exist for the current product design. These should be added independent of what relation they have to customer requirements.

The Main Floor

Now back to the main floor. This is where we make the connections between the customer requirements and the design characteristics. The purpose of this room is to holistically assess how well a customer requirement maps to certain performance characteristics. As an example, the maneuverability requirement would strongly correlate to the “weight” design characteristic but have little correlation to how loud the cleaner was (“sound”) or whether or not it has a modern aesthetic. This part of the house will look very familiar to anybody who has ever used a cause-and-effect matrix for process improvement.

The Roof

Finally the roof. This is the most interesting and insightful part of the house of quality. Similar to the main floor we just toured, the purpose of the roof is to assess different design aspects using the information acquired in the main floor assessment. However, whereas the main floor correlated to the design aspects with the customer requirements, the roof seeks to identify correlations the design components themselves. We might see that weight and durability are highly and positively correlated, but weight and maneuverability are negatively correlated (e.g., the heavier an object is), the harder it is to maneuver.

What QFD users will see is that a number of tradeoffs exist between what the customer requires and what the current product design can deliver. As an example, take a consumer tire for a vehicle. As shown in the fully completed, albeit simplified, house of quality in Figure 2, the customer desires five things: quiet ride, good gas mileage, longevity, cost and safety/handling. Upon closer examination, the desires of the customer as plotted in the house matrix show the conflict between design and customer wants. A tire that has a quiet ride will use softer rubber and wear away quicker. A tire that lasts for 80,000 miles will sound like you’re driving on the Flintstone’s first set of tires. Good gas mileage usually means a lighter tire with less material, which leads to both a less comfortable ride and a shorter product lifespan.

Figure 2: House of Quality for a Consumer Tire
Figure 2: House of Quality for a Consumer Tire

The roof of the house shows also shows how the design considerations interact with one another, independent of anything the customer wants. In this instance, there are strong correlations for weight for tread thickness and tread width. This strong correlation leads to a tradeoff between good gas mileage (low weight) and a quiet ride (thick tread, wide tires). The design dictates the tradeoffs a customer is going to face.

Many houses of quality have a right wing of the house, which is used to compare how well competitors perform in the CTQ-VOC requirements. This provides more information for product developers to identify and prioritize gaps.

The Basement

What’s most glaringly absent in this house of quality is the basement. The basement is essentially a weighted average of the relative importance of each customer requirement and the relative performance of each design characteristic. The reason this is such a glaring absence is because QFD is not made up of just one house of quality, but several.

The standardized progression of HoQ for QFD is:

Customer requirements x design specifications

Design specifications x engineering requirements

Engineering requirements x process planning

Process planning x production and quality control

In each of these cases, the same QFD approach is used to understand the needs of the upstream customer and what adjustments and specifications must be realized by the supplier. To seasoned Lean readers, you may notice some remnants of Hoshin Kanri policy deployment. Starting at a high level with a customers needs, we deploy the plan of increasing specificity that will result in high quality for each part of the process. The basement tells us which are the most important design characteristics to bring into the next house of quality. 

The Voice of the Customer

Like so many other tools in the Lean toolbox, the house of quality’s value comes from the focus it provides. The house of quality methodically structures design thinking around the product based on VOC. It prioritizes the customers’ needs. The house of quality becomes the key to unlocking value for our customers. If a new design of process or product can reduce the tradeoffs identified in the house of quality, more value is delivered to the customer. This is innovation.


As an example, take the first iPhone. The first iPhone revolutionized cell phones lead the way to the era of smart phones. Let me argue, though, that the most innovative thing about the iPhone wasn’t the software, apps or the internet. The most innovative part of the iPhone was its physical design. For the first time ever, the screen was the size of the phone.

Just about every phone adheres to this dominant design that features no physical keyboard and a large touchscreen. Why was Apple able to create this innovation where other dominant competitors, like Blackberry, couldn’t? Up until this point there was no dominant design for a cell phone. Cell phones could flip open like the Motorola Razr or slide open to reveal a keyboard. The conventional wisdom was that in order to text or type on a phone you either had to have a full keyboard or tirelessly type on the telephone keypad. Blackberry owes its early success to this paradigm. It was one of the first manufacturers to give consumers a full keyboard and a screen.

The obvious tradeoff in this paradigm, as the house of quality would reveal, is between cost, size, keyboard and screen size. In order to have a phone with both a large screen and a keyboard, the manufacturer would have to make a very expensive, very large phone. Take away either the larger screen or full keyboard and the product loses its functionality. Customer satisfaction dwindles. These are the tradeoffs Apple identified and exploited. By focusing on these design tradeoffs, Apple’s team got to work brainstorming ways to remove them. Their effort ultimately culminated in a phone that had a touch-screen over its entire surface and used an on-screen keyboard in lieu of a mechanical one.

This innovation led to other opportunities for auto correcting and recommending words – reducing the time to send a message and increasing user satisfaction. It further reduced the complexity of phone. While blackberry had upwards of 40 buttons, the iPhone had five. The touchscreen-centric design of the first iPhone shifted the paradigm of the cell phone industry and ushered in a new era with a new dominant design.

By following the approach of QFD and the house of quality, innovators can focus on the boundaries of the current paradigm. This intense focus pulled by the VOC is what allows innovators to make radical changes. Their efforts are highly impactful. The new approaches they come up with to remove or alter the tradeoffs of design deliver radically new value propositions that delight the customer.

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