TGFR Consulting LLC Feature Development and Performance Parameters
Feature Deployment maps the VOC statements to a set of device features to be used as part of the QFD process. An effective mapping effort creates a minimum set of performance parameters, sufficient to allow the QFD to be effective. Developing the minimum set of performance parameters drives more effective execution of the QFD process. Populating the columns of the QFD with this minimum set of parameters simplifies QFD execution and the subsequent results do a much better job identifying the key CTQs (critical to quality features) for the product.
Specifically, a performance parameter adheres to the following definition
A performance parameter represents the definition of a tangible/measurable deliverable of the future product.
Performance parameters are measureable. Performance parameters have a range of values. The ability to vary the range of a parameter represents the key discriminant for performance parameters. A required feature may be important, but without the ability to vary over a range this feature cannot bet a performance parameter to be be used in QFD process. This discrimination can be summarized as the following key concept
All performance parameters are features, but not all features are performance parameters.
In developing performance parameters, care must be taken not to assume a particular implementation. At this point in the process, a future product concept has yet to be defined. Features should not assume anything related to implementation. A key tool that can help with the development of an implementation-free set of parameters is the standard fishbone (Fishbone (Ishikawa) Diagram, n.d.) diagram. Use of the fishbone diagram facilitates the general mapping from a user need (the effect) to the features or performance parameters that will be used in the QFD process. The fishbone provides the framework and structure around determining how features contribute to the user need. A traditional fishbone contains the following generic groups of contributing features
- Methods – The use cases associated with the use of the product
- Associated Equipment – other equipment associated with the use of the product.
- User – the skills and training of the users
- Materials – the material involved in the device
- Measurement – the accuracy of the device during operation
- Environment – this would be the operating environment for the product
These categories make up the branches of the fishbone, and often these generic grouping can help push the brainstorming to consider all areas where features may impact the user need. Care should be taken to limit the brainstorming to these general categories, as often other features that don’t easily fit into these generic groups will be identified.
This fishbone process allows the identification of the minimal number of features that influence satisfaction of the VOCs. Only those features directly contributing to the VOC are identified, with extraneous features ignored. While other features may be identified later in the requirements design, only features directly influencing user needs should be considered for use in the QFD process. Features that are attributes, without the ability to have a range of values can be identified and omitted from the final list of performance parameters. Attribute features will be important in the development of the final concept or design, but these features do not serve as discriminating parameters for the QFD (more on this later).
The following example shows a partial fishbone diagram associated with a VOC need
I need the patient to receive the exact prescription ordered by the doctor
Fishbone of User Needs
In this example, two features, “Number of transactions between doctor and medication delivery” and “level of authentication for access to prescription” have been identified as part of the contributing features. The “level of authentication for access to prescription” represents an attribute, as the parameter cannot be varied due to regulatory considerations. The performance parameter is “number of transactions” and the measureable range would be between 1 to 4 transactions.
Following the fishbone drawings/analysis for all of the VOC statements, the resulting full set of performance parameters are coalesced into a single, unique list. Often a single performance parameter contributes to a number of VOC statements, and in coalescing the list all duplicates should be removed. During the QFD process the impact of a single performance parameter will be reflected in the values within the QFD matrix.