Mastering Critical-to-Quality in Six Sigma

Six SIgma CTQ

Six Sigma’s process improvement technique is built around clear goals and uses measurable metrics; it provides clear, goal-driven road maps for making business processes more efficient, consistent, and economical. When your customer asks for ‘better’ processes, what does that mean? How can you realize it in the process? 

Critical-to-Quality (CTQs) are the missing link between your customer’s abstract concept of ‘better’ and a concrete, understandable, measurable, and practical way to improve the process so that it really is ‘better’. 

CTQs give you something concrete and measurable to aim for—guaranteeing that your process improvement efforts actually hit the mark. This article covers the definition of CTQs, what they are, why they matter, and how they fit into the Six Sigma methodology.

Identifying CTQs Through Voice of the Customer (VOC) Analysis

The Six Sigma method centers around understanding what customers need, and CTQs convert vague customer desires into quantitatively trackable targets. But, how do we find these CTQs? 

We tap into the Voice of the Customer (VOC), which essentially means listening to what your customers are saying.

Here’s how to identify CTQs through VOC analysis:

Step 1: Gathering Customer Intelligence

Get started by gathering the data to examine. 

  • Customer Surveys and Interviews: Direct conversations are a goldmine for giving you a first-hand look at what frustrates your customers and what they truly value.
  • Focus Groups: Get a group of customers together to brainstorm. The energy is contagious, and you might hear things you wouldn’t in one-on-one chats.
  • Customer Complaints: Treat complaints like a roadmap to improvement. They highlight areas where your processes are falling short and where CTQs can have a big impact.
  • Warranty Data Analysis: Warranty claims expose weaknesses in your products or services that directly affect customer satisfaction. Here’s your chance to identify areas where CTQs can make a real difference.

Step 2: From Data to Actionable Insights

Next, we transform this VOC data into actionable CTQs.

  • Affinity Diagrams: Group similar customer concerns together to reveal recurring themes. This helps you identify the most prevalent wants.
  • Prioritization Matrices: Not all customer needs are created equal. Assign weights to customer requirements based on their importance and frequency. This helps you focus on the CTQs that will give you the biggest impact.

Step 3: Prioritizing for Impact

Remember, customer needs are a spectrum. Here’s what to consider when prioritizing CTQs.

  • Frequency of Mention: Pay attention to what customers bring up the most during VOC analysis. Those are likely high-priority CTQs.
  • Impact on Satisfaction: How much happier would customers be if you addressed a specific need? Analyze the impact on customer experience.
  • Feasibility and Cost: Be realistic. Can you technically and financially meet these CTQs? Some improvements might be too expensive or have technical hurdles.

Strategically prioritize CTQs based on these factors and your Six Sigma quality improvement projects will target the most impactful issues, ultimately leading to happier customers.

Tools and Techniques for CTQ Definition and Measurement

Let’s explore the Six Sigma tools that help us define and measure these critical customer needs effectively:

ToolDescriptionBenefit for CTQs
Quality Function Deployment (QFD)This structured approach translates customer requirements into measurable technical characteristics. It helps identify the relationship between CTQs and design parameters, ensuring the product or service meets customer expectations.Breaks down broad customer desires into specific, measurable engineering requirements.Ensures CTQs directly translate to product or service features.
Kano Model AnalysisThis model categorizes customer requirements into five types: Basic Needs (must-have features), Performance Needs (the more the better), Excitement Needs (unexpected delights), Indifferent Needs (features with no impact), and Reverse Needs (features that can cause dissatisfaction). By analyzing CTQs through the Kano Model, project teams can prioritize efforts.Helps prioritize CTQs based on their impact on customer happiness.Identifies opportunities to exceed customer expectations with “excitement needs.”
Critical Path Analysis (CPA)CPA is a project management technique used to identify the sequence of tasks that are essential for project completion.Not directly applicable to CTQs, but can be used in conjunction with CTQ-related activities within Six Sigma projects to ensure efficient task scheduling.

Implementing CTQs in DMAIC Methodology

Six Sigma uses DMAIC (Define, Measure, Analyze, Improve, and Control) to drive process improvement. CTQs are essential throughout each stage, keeping the focus on what matters to your customer:

Define and Measure: Setting the Stage 

  • Define: First, we clearly define the problem and what we want to improve. CTQs become our measurable targets for success, making sure we’re all focused on what truly matters to customers.
  • Measure: We then gather data to see how things are currently working in relation to each CTQ. This data becomes the starting point for measuring future improvements.

Analyze: Unveiling the Root Causes

  • Analyze: We analyze the connections between CTQs and different process variables. This helps us pinpoint the factors most likely to cause issues with meeting our CTQ targets.
  • Not all problems are equal. We use our understanding of how CTQs impact customer satisfaction to prioritize what to tackle first. We focus on addressing the root causes that will have the biggest positive impact on meeting our CTQ goals.

Improvement and Control: Delivering the Results

  • Improvement: Now that we know the root cause, the team develops and implements solutions to address these issues and improve CTQ performance. By focusing on eliminating the root causes that most significantly impact CTQs, the team ensures that the changes they make have a real and measurable impact.
  • Control: The final step makes sure the improvements last and sets the stage for continuous improvement. Processes are standardized and monitored to keep CTQ performance consistent. Regular data collection allows the team to catch any potential problems and take corrective action to keep CTQs within acceptable ranges.

Case Studies: Successful Applications of CTQ in Six Sigma Projects

CTQs are important in theory, but how do they translate into real-world wins? Here are a few examples:

Scenario 1: Reducing Delivery Times in Online Retail

Problem: A retailer is struggling with high customer churn. Their delivery times are frustratingly slow, leading to customers taking their business elsewhere.


  • Order fulfillment time (measured in hours)
  • On-time delivery rate (percentage)

Solution: By focusing on these CTQs, the Six Sigma experts were able to document inefficiencies in the order fulfillment process, such as a cumbersome picking procedure and a less-than-optimal warehouse set-up. They implemented changes such as a revised picking procedure and a redesigned warehouse set-up that cut fulfillment times in half and increased the rate of same-day deliveries to 90%. 

Result: The team satisfied the company’s key customers by rapidly reducing fulfillment times and increasing the percentage of on-time deliveries, and were able to lower churn rates.

Scenario 2: Enhancing Customer Satisfaction in a Call Center

Problem: A call center has long wait times leading to frustrated customers. It has a high call abandonment rate and has been slammed with negative customer reviews.


  • Average call handling time (measured in minutes)
  • First call resolution rate (percentage)

Solution: The Six Sigma black belts and green belts analyzed the call center from a set of CTQs, and made improvements such as better agent training and efficient routing of the caller’s issue, which reduced the average call-handling time and increased the rate of issues resolved on the first call. 

Result: Customers became happier; there were fewer abandoned calls and more five-star online customer reviews.

Scenario 3: Optimizing Manufacturing Processes for Improved Product Quality

Problem: A manufacturing company was experiencing a high rate of production defects, with many customers making complaints and returning products.


  • Number of defects per unit
  • Customer return rate (percentage)

Solution: Six Sigma professionals studied the manufacturing process to identify the root causes of defects in order to arrive at solutions such as better quality management procedures and adjustments to machine settings so that the percentage of good products increased. This drastically cut back the number of defective products and customer returns to the manufacturer. 

Result: Satisfied customers meant a stronger brand reputation and therefore an increase in profitability.

Challenges and Best Practices in Managing CTQs

CTQs are undeniably powerful tools for driving quality control and process improvement in Six Sigma projects. However, implementing them effectively necessitates a nuanced approach. 

This section explores the key challenges associated with CTQ management and outlines best practices for overcoming them.

Challenge #1: Balancing Conflicting CTQs and Stakeholder Alignment

Finding the CTQ sweet spot is quite the challenge. Customers often crave speed and convenience, reflected in lower CTQ values like faster delivery. But that can clash with the need for thorough quality checks, potentially slowing things down. This creates a CTQ tug-of-war. 

It’s not just customers either–internal teams might have different goals. Balancing customer needs with production efficiency or cost-cutting efforts can be a delicate dance, requiring careful consideration of all stakeholders’ priorities.

Best Practices:

  • Open Communication: Foster a culture of open communication with both customers and internal stakeholders. Explain potential trade-offs between different CTQs and work collaboratively to find solutions that strike an optimal balance.
  • Prioritization Power: Utilize the Kano Model or similar techniques to prioritize CTQs based on their impact on customer satisfaction. This helps focus efforts on the CTQs that truly matter.
  • Win-Win Solutions: Get creative. Can you implement faster inspection methods that enable both thorough checks and quicker deliveries?

Challenge #2: Ensuring Measurement Accuracy and Consistency

Inaccurate or inconsistent data leads to shaky foundations and ultimately, project failure. Clarity is the remedy; Ensure your CTQs are clearly defined with specific, measurable units. Think “number of defects per unit” instead of just “good quality.” 

Also, everyone needs to be on the same page about what they’re measuring. Standardize your data collection and analysis techniques across the organization. This ensures everyone is using the same ruler, so to speak, and that your CTQ measurements are consistently reliable.

Best Practices:

  • Training for Accuracy: Provide adequate training to staff responsible for CTQ measurement. This ensures everyone understands the definitions, protocols, and the importance of accurate data collection. Consider Six Sigma belt certification for those working on the project to ensure they have a deep understanding of process improvement with data.
  • Data Verification: Establish a process for data verification to identify and correct any inconsistencies or errors in CTQ measurements.
  • Statistical Support: Utilize statistical tools to analyze measurement variability and identify potential outliers that could skew your data.

Conclusion: Leveraging CTQ Principles for Process Optimization and Quality Excellence

CTQs are an essential part of every customer-centric Six Sigma and Lean Six Sigma project. They translate what customers want into action by establishing targets for process optimization so that, in the end, quality excellence is the result. However, CTQs are not perfect. There will likely be contradictory CTQs that need to be balanced, and measurement parameters will need to be consistent.

Open-minded companies that listen to customer feedback and get different teams talking can create CTQs that are both meaningful and achievable. The result is a Six Sigma quality improvement project with real value for everyone—better-optimized processes and happier customers.

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