Critical to Quality (CTQ)

What are CTQs?

Critical-to-Quality (CTQ) is the essential aspect of a product or service that directly affects customer satisfaction. CTQs are essential in defining project goals and ensuring that the output meets or exceeds customer expectations. Identifying and addressing CTQs is crucial for process improvement and achieving Six Sigma’s goal of reducing defects and variability. The Six Sigma project team determines the CTQs during the Define phase of the DMAIC.

Key points to understand about CTQs:

  1. Customer Perspective:

    CTQs are identified from the perspective of the customer. These are the critical characteristics or parameters that customers care about and directly influence their satisfaction.

  2. Measurable Parameters:

    CTQs are specific, quantifiable, and measurable parameters evaluated objectively. This ensures the project team’s improvement efforts are focused on concrete and meaningful goals.

  3. Input to Output Relationship:

    CTQs represent the key inputs to a process that directly impact the desired output. By controlling and optimizing these inputs, the organization can improve the process to consistently deliver the desired results.

  4. High Impact on Quality:

    CTQs have a significant impact on the quality of the final product or service. Improving these critical factors can lead to a noticeable enhancement in customer satisfaction and a reduction in defects.

  5. CTQ Tree:

    A common tool used in Six Sigma projects to identify and map CTQs is the CTQ tree. It helps break down high-level customer requirements into more specific, measurable CTQs and further links them to specific process inputs.

  6. VOC and VOB:

    Organizations often derive CTQs from the Voice of the Customer (VOC) and convert them into the Voice of the Business (VOB). VOC represents customer needs and requirements, while VOB translates those requirements into measurable and actionable metrics.

  7. Benchmarking:

    Frequently, organizations benchmark CTQs against industry standards or best practices to establish meaningful targets and measure the process’s performance.

Example of CTQ:

Let’s take an example of a project focused on reducing customer order to delivery cycle time. The project has three requirements, and we’ll explore how to develop the appropriate measures for each requirement.

  • The first requirement is to reduce the order to delivery time, and the CTQ here could be cycle time since it measures time.
  • The second requirement is to have correct customer addresses, so the CTQ here could be customer address errors.
  • The third requirement is to streamline the process, and you can use CTQ like lead time or value-added time.

It’s important to note that each CTQ should be quantitative and directly linked to a specific requirement, ensuring a clear connection between the two.

Differences between metrics and CTQs:

Critical to Quality (CTQ)

Relationship between Metrics and CTQs:

  1. Identifying CTQs:

    The first step in determining metrics is to identify the CTQs. CTQs help define what aspects of the process or product are critical to customer satisfaction. Once you establish the CTQs, you can select appropriate indicators to measure and track those critical characteristics.
  2. Setting Targets:

    Organizations use metrics to establish targets or acceptable ranges for the CTQs. These targets represent the level of performance required to meet customer expectations.
  3. Monitoring Performance:

    Organizations use metrics to monitor the performance of the CTQs over time. By tracking these measurements, they can ensure that customer requirements are consistently met and necessary corrective actions are taken.
  4. Process Improvement:

    Metrics provide data-driven insights into process performance, helping organizations identify areas for improvement related to the CTQs. They help prioritize improvement efforts based on their impact on critical quality characteristics.


When developing critical quality metrics for your projects, make sure to consider all requirements and refer back to the voice of the customer. There should be a clear connection between what you’re measuring and what you’re trying to improve for the customer. For instance, if you’re creating a door, consider factors like what needs to fit through the door, required clearance, intended accessibility, users of the door, their size and ability, and whether a lock or window is necessary. Answering these questions based on the voice of the customer and their key requirements is essential.

Key takeaways:

  • Critical-to-Quality (CTQ) is vital for customer satisfaction and project success.
  • Customer Perspective: CTQs reflect what customers care about and impact satisfaction.
  • Measurable Parameters: CTQs are specific, quantifiable, and objective.
  • Input to Output Relationship: CTQs are key process inputs linked to desired outcomes.
  • High Impact on Quality: Improving CTQs enhances quality and reduces defects.
  • CTQ Tree: A tool to map customer requirements to measurable CTQs and process inputs.
  • VOC and VOB: CTQs derived from Voice of the Customer (VOC) and translated to Voice of the Business (VOB).
  • Benchmarking: Compare CTQs against standards for target setting and performance measurement.
  • Metrics vs. CTQs:
    • CTQs define critical aspects of customer satisfaction.
    • Metrics measure and track CTQs to meet targets and improve.
  • Process Improvement: Metrics guide process enhancement based on CTQ impact.
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