Hi Jacob, you’ve provided a great definition of what makes an effective design input. There’s actually a mechanism that Dr. Simon discussed this week in the lecture.

To turn a qualitative design goal into a quantitative result, you need to consult the customer on what they specifically want. This is accomplished via the DID (“Design Input Document”). This form is used by Marketing to help the client define what the product is intended to do and how. This consists of desired dimensions and intended functions. Using that information, engineers can translate those constraints into quantifiable/measurable values in a DSD (“Design Specification Document”), defining dimensions, materials, constraints, and design plans. In other words, it turns qualitative into quantitative. 

To ensure that the design inputs can be referenced back to the initial purpose, always take meeting minutes. This has been discussed at length in a good portion of the threads, starting with Dr. Simon himself. I have replied to another thread on this matter, but I will reiterate: meeting minutes are a useful tool to log significant portions of a meeting, especially when discussing subjects like design reviews/controls. This gives professionals the ability to keep tabs on a project’s progress through crucial milestones and data, especially during times when that info may not be as readily available without reference. With well-maintained meeting minutes, a team can effectively track their consistency through the life of the project, making sure they are following the path they set in a way that meets (and exceeds) customer expectations.

I like how you mentioned the importance of using documents like the DID and DSD to turn user needs into measurable specs. Something that also works great for bridging that gap is Quality Function Deployment (QFD) which is basically the “House of Quality” method. It helps take broad user feedback (like easy to clean or lightweight) and turn it into clear and testable design targets, such as specific weight limits or surface finish requirements.

What I like about QFD is that it shows the connection between what users say they want and what engineers actually build. It’s visual, structured, and it automatically keeps that traceability everyone’s been talking about. In addition, by ranking which user needs matter most, it helps teams focus on the features that impact usability and satisfaction, not just what’s easiest to design.

The responsible persons have to research and collect data on user needs. They have to understand the user’s procedures and identify the risks & effects of the product. External factors like individual user performance can influence the product. This information can be obtained in various ways whether that is through interviews, surveys, or a combination of methods. A medical device company may have a standard template with requirements that a customer provides via a master form. A Project Initiation Request (PIR) is one example, and can be used to further develop the user needs, which then turns into quantitative design inputs for a DID. Documenting user needs complies with regulations and provides a clear and unambiguous structure for design inputs, thus traceability is maintained. 

In order to translate the user needs to design inputs, it requires the involvement of multiple departments such as marketing, engineering, quality, and regulatory. Medical device standards, guidelines, and regulations guide design inputs. Verification tests are made during the design & development process which will later support the functionality and specifications of the design outputs against the design inputs. The roles and responsibilities for design inputs and outputs are documented in a DDP. A design verification plan and report can be made as well. 

The best way to translate a qualitative user need into a testable and quantitive design input is by breaking it down into measurable criteria. To maintain traceability, teams can utilize a design traceability matrix thank connects each user need to its corresponding design input, validation activity, and verification test. This ensures that every design decision can be traced back to the initial requirement, assisting in confirming that the final product truly meets the user's expectations.

Others have already mentioned specifics of using documents like the DID, and DSD to turn broad user needs into specific device specifications. However, I believe that more generally speaking, anything that ensures the robustness of the feedback loop is the best way to translate qualitative user needs into quantitative specifications. These documents as well as the verification process of ensuring design inputs have maintained traceability are all ways to ensure that feedback makes its way into the design. Essentially the best way to translate customer requirements into design specifications, is to make sure that the feedback loop is able to properly function so that iterative improvements can be made to the design to bring it closer to the customer's vision while still getting the specificity needed. 

From working at my coop, I realized that the customers usually have many wants and they are usually not all realistic because they are simply asking for too much. Because of that there is a need for a clear conversation that shows what is possible and what is not because a certain feature may be wanted, but having to quantify it every time would simply be impossible because it is hard to measure or it would require another new machine to be able to actually measure it. So, the best way I have seen is understanding what the customer wants but then pushing back to meet somewhere in the middle because it is not just about keeping the customer happy, but it is about accepting realistic wants. It involves a lot of creative thinking because you have to try to meet customers' most of the way but still make the process easy for you to complete. I agree with the comment about a robust feedback loop because that is probably the simplest way of meeting the needs of customers because it will help to make adjustments a lot faster. Especially because the quantity of the pieces is not usually small, but since it can be hard to measure every piece a feedback loop helps to locate discrepancies and then allow for adjustments right away. Overall, I think that it is about understanding what the customer wants but finding creative methods of actually being able to meet those needs and sometimes even offering a simple alternative and introducing a feedback loop that can be easily made and applied quickly. 

I think that defining "success" in quantifiable terms is the first step to converting a qualitative user need into a quantitative design input. If a user requests that a device should be easy to clean you could decide that all surfaces must be within reach of a cleaning instrument of a specific size or that the device can be dismantled easily in less than a specific amount of time. For verification I would utilize a requirements traceability matrix that directly connects each design input to the initial user demand in order to maintain corresponding needs so that I can demonstrate how each specification is linked to a legitimate requirement and how verification tests are intended to ensure that needs are satisfied. This would guarantee that nothing is lost between user expectations and the finished design.

The best way to translate a qualitative user need into a quantitative design input is to break the need down into measurable characteristics using engineering standards, research, and benchmarking. For example, if a user states the device must be easy to clean, engineers can convert that into a measurable requirement such as withstand disinfection using 70% isopropyl alcohol for 100 cycles without material degradation or discoloration. Another helpful strategy that I was able to witness in industry is conducting field observations, and reviewing relevant standards to define precise performance criteria. Once those quantitative inputs are established, documenting them in a matrix helps maintain clarity and consistency. To verify traceability, each design input should be linked back to the original user need through a traceability matrix, ensuring no requirement is lost or misinterpreted. Testing protocols should then be written to evaluate whether the product meets each quantitative requirement. 

The best way to translate a qualitative user need into a quantitative and testable design input is to follow an iterative process of user analysis, measurable criteria definition, and engineering translation. First, the design team should clarify the intent behind the qualitative need through user interviews, observations, or task analysis to understand what the user truly means. For instance, if a user says the device should be easy to clean, the team identifies what “easy” implies in practice. This insight is then converted into measurable requirements, such as defining the cleaning time, number of tools required, surface roughness, or disassembly steps. These design inputs must be objective, testable, and aligned with standards. To ensure traceability, a design traceability matrix is used to map each user need to its corresponding design input, design output, verification test, and validation step. Maintaining this matrix throughout development ensures that every design input remains linked to its original user need, and that verification and validation activities confirm both compliance and user satisfaction.