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QFD Summary |
Quality function deployment (QFD) is a method to ensure that the “voice of the customer” is considered when determining a product’s requirements. It was introduced in Japan for the manufacturing sector during the 1960s by Dr. Yoji Akao as a successor to the concept of Total Quality Control. QFD was introduced to America and Europe in the early 1980s.
Compared to other methods of qualitative validation, QFD judges quality based on the system’s ability to meet the customers’ needs instead of judging quality based on the number of defects. QFD assumes that the customer has known and unknown needs and the system should address both.
QFD provides a graphic tool known as the “house of quality” to compare customer requirements, both stated and unstated, technical requirements, proposed technical features, the current product, the competitors’ products, and the current market conditions in order to determine technical elements which the new system should have. Proposed technical features are evaluated in terms of their ability to meet the customer requirements and are further prioritized based upon the rank of the requirements. This information is then compared against the current product’s ability to meet the requirements and the competitors’ ability to meet the requirements. Furthermore, the proposed technical features are evaluated in terms of their marketability. Once the “house of quality” has been completed each opposed technical feature is given a priority.
The QFD process includes a team of 5 to 8 individuals from management, marketing, product and development, and product support areas. There are four phases to the process including product planning, product design, process planning, and production. Each of these phases has a final deliverable with acts as an input to the next phase. The QFD process includes seven management tools: the affinity diagram, the tree diagram, the matrix diagram, the prioritization matrix, the interrelationship diagram, the process decision program chart, and the activity network diagram. The affinity and tree diagrams are methods to organize requirements. The matrix diagram, prioritization diagram, and interrelationship diagram show relationships between multiple items. The process decision program chart is a means to plan for risks. The activity diagram is a method of scheduling tasks.
QFD was modified in 1989 by Betts in order to be able to apply it to the software development cycle. The “customer voice” translates to the system’s objectives and the technical features translate into a high level design. Other extensions to QFD include Blitz QFD, which includes only the essential components of QFD, and Distributed QFD, which allows a QFD to be accomplished by distributed teams.
The strengths of QFD include: increased customer satisfaction with the final product, reduced development on features which add little value, a means for the external customer to provide feedback, a means for internal communication between different disciplines, documentation, lower product cost, and requirements traceability. The weaknesses of QFD include: QFD can be a complex method to adopt, the assumption that the requirements will be fully determined at the beginning of the project development cycle and that they will not change during development, the assumption that market analysis data is available, and the lack of stakeholder involvement. Due to the weaknesses outlined above, it is suggested that QFD is beneficial to a limited set of projects where competition is high and market data is readily available, customer satisfaction is paramount, administrative tools are available, and the project is complex.
The exercise was to do an affinity analysis and populate the QFD house of quality with the set of requirements and importance ratings given below:
"A major supplier of digital devices needs to upgrade one of its products, a palm pilot. They found they were losing business because their competitors, in some extent, are already one generation ahead of their current product."
Affinity Analysis
QFD House of Quality
| QFD vs. Cleanroom | While both the Cleanroom process and QFD focus on quality, the definition of quality differs. In Cleanroom, quality is primarily measured through formal mathematical and statistical validation against the requirements, whereas QFD focuses more on quality from an organizational or customer's viewpoint with the focus on value provided instead of the number of bugs per lines of code. |
| QFD vs. SASD | While both QFD and SASD focus on customer requirements, QFD is primarily interested in determining requirements at the high level and setting product goals. It assumes that the product being developed will be marketed competitively. On the other hand, SASD assumes that the system’s high level goals have already been defined. SASD provides a modeling technique for taking a high level idea of requirements and decomposing them into smaller components. |
| QFD vs. JAD/PD | QFD and JAD both focus on setting the system’s requirements based on the users’ and stakeholders’ needs. QFD does not provide a means for eliciting the requirements from the users and stakeholders while JAD does. Moreover, QFD assumes that the system is being developed for competitive purposes and therefore the users are external to the organization, while JAD does not make these assumptions. |
| QFD vs. Agile Processes | While both QFD and agile processes in base their philosophy on customer satisfaction, they have little in common. QFD primarily focuses on requirements selection based on competitive analysis and does not address the development cycle nor does it provide a means to validate the designed product against the customers’ is wishes. Agile processes, however, assumes customer involvement in the whole software development cycle thus addressing customer requirements throughout the project. As well, agile processes do not exclude systems which are not being developed for competitive purposes. |
The main strength of QFD is in providing a means to examine the proposed system in terms of its benefits to the organization and based upon competitive positioning. As such, there is a lower likelihood that systems or features will be developed because they are “neat” or “fun” but which provide little value to the end customer and thus to the sponsoring organization.
A second strength of QFD is that in order to complete the house of quality, management, marketing, and technical development must discuss and examine the proposed system. This provides a means to transfer knowledge between the three parties involved.
A major weakness of QFD is in its assumption that the system under development will be marketed. Therefore, this method would not be appropriate to a number of development projects such as public works systems or systems which will remain internal to the sponsoring organization.
A second weakness of QFD is that covers a limited scope of the software development life cycle. As such, it is possible the software professionals would overlook this technique in favor of other methods which provide more support for the whole project. If this technique were to be used, it would need to be used in conjunction with other requirements analysis and software development methods.