Harnessing the Voice of the Customer in Six Sigma: A Comprehensive Guide

Voice Of Customer Six Si

Use this guide to learn the benefits of harnessing the Voice of the Customer (VOC) in Lean Six Sigma and understand data gathering and analysis tools used to support process improvement.

Voice of the Customer (VOC) fits within Six Sigma

Process improvement to gain excellence in product or service delivery is the primary driving force of Lean Six Sigma. Within Six Sigma, the Voice of the Customer (VOC) represents the customer’s explicit and implicit needs, desires, and expectations.

Understanding the Voice of the Customer

Voice of the Customer (VOC) grew from Six Sigma projects to identify process improvement points from the point of view of the most essential person in any business engagement: the customer.

Voice of Customer Six Sigma Definition

VOC describes how understanding the customer’s expectations and needs enables improvements aligned with customer requirements.

Voice of Customer Example | Customer Comment Posted for Online Purchase

VOC data collection can be as simple as a feedback form. For example, the customer feedback forms for Amazon.com purchases provide sellers with VOC data.

“I purchased this mini blender to help me eat healthier, but I hate how hard it is to clean, so I don’t use it anymore.”

With this example, insights may lead to:

Organizing customer data to determine needed process changes leads to the Critical-to-Quality metrics.

Critical-to-Quality (CTQ) Metrics

CTQ (Critical to Quality) describes the measurable characteristics of a product or service. In Six Sigma, CTQ metrics bridge the Voice of the Customer and improvement initiatives.

Steps to derive CTQs from VOC data

Translate your VOC data into tangible CTQ metrics, ensuring that organizational efforts align directly with customer expectations with these steps:

  1. Gather VOC data from reliable sources for accurate customer representation.
  2. Analyze VOC data to identify common themes within customer needs and complaints.
  3. Convert VOC themes into specific, measurable, and relevant CTQ statements.
  4. Rank CTQ statements based on their importance and feasibility.
  5. Organize CTQ statements into quality categories to inform any needed action.

Returning to our example VOC feedback example, a derived CTQ requirement is: 

VOC StatementImplicit Customer NeedCTQ Requirement
“…I hate how hard it is to clean, so I don’t use it anymore.”Cleaning equipment should be easy and fastEase of Use

VOC in Define, Measure, Analyze, Improve, Control within Six Sigma Projects

The project charter that reflects the VOC, outlining CTQ metrics to focus on during the DMAIC (Define, Measure, Analyze, Improve, Control) process, better ensures improvement initiatives driven by customer needs. In the Define phase of DMAIC, translate VOC into actionable CTQ metrics by:

Incorporating customer feedback loops into the DMAIC cycle

Define Phase

  • Clearly articulate the customer’s problem or opportunity.
  • Identify the customer group/s and their requirements.
  • Determine when the customer feedback (data) should be collected in the customer journey.

Measure Phase

  • Develop metrics that reflect customer expectations.
  • Gather data on current performance related to CTQs.
  • Establish a baseline for further analysis.

Analyze Phase

  • Analyze the collected data to identify patterns over time.
  • Prioritize CTQs based on their impact on customer satisfaction.
  • Use tools like Pareto charts to highlight critical areas for improvement.

Improve Phase

  • Develop solutions that directly address prioritized CTQs.
  • Validate improvements with customer feedback.
  • Implement changes to product/service and monitor their impact on the CTQs.

Control Phase

  • Establish control measures to sustain improvements.
  • Continuously monitor and measure CTQs to ensure ongoing customer satisfaction.
  • Implement feedback loops to adjust processes based on changing customer requirements.

Integrating customer feedback loops into the DMAIC cycle creates a responsive approach to process improvement.

VOC data collection methods and data types

Within Voice of Customer Six Sigma projects, proven feedback collection tools for alignment with customer needs include surveys, focus groups, customer interviews, direct observations, sales data, social media monitoring, and customer service interactions.

Explicit and implicit customer

Customer feedback can take explicit forms, such as direct complaints or praise, but it also exists implicitly within customer behavior and usage patterns. Recognizing and understanding both conditions is crucial for a holistic VOC strategy.

Explicit customer feedback

Explicit customer feedback is straightforward information the customer knows they are giving to the business about a specific product or service. Explicit customer feedback tools include:

  • Social media monitoring
  • Customer feedback surveys
  • Focus Groups

Implicit Customer Feedback

Implicit customer feedback is up to interpretation and is not given directly from the customer to the business. Implicit data gathering tools include:

  • Sales data (e.g., demographics, how purchased, when purchased, if returned, or how long items stayed in the online cart before purchase)
  • Referrals (e.g., Net Promoter Score data)
  • Support tool engagement (e.g., how often help bots or tech support is engaged, the category of customer service questions, the quantity of customer service questions)

What is likely the most impactful of all implicit feedback? When your customer stops buying from you. While that customer probably did not tell you directly that they are no longer your customer, their action does inform you of the decision.

Example Explicit and Implicit Data

Returning to our example customer comment, it contains explicit and implicit feedback as listed:

“I purchased this mini blender to help me eat healthier, but I hate how hard it is to clean, so I don’t use it anymore.”


  • Purchased to help with a healthy lifestyle.


  • Purchased for self.
  • Shipping and arrival met expectations.
  • Time to clean is part of the requirements for satisfaction.

Tips for effectively collecting VOC data

To ensure that the feedback accurately represents customer expectations, organizations should:

  • Avoid inherent bias in design (no leading questions like “you like our product because…”).
  • Be consistent in design to build reliable trend reports over time.
  • Gather data from different customers for a holistic approach indicative of all customers.
  • Update collection methods to address customer behavior or market changes.
  • Utilize quantitative and qualitative data.
  • Validate the feedback from cross-referencing with other data sources like sales data, industry trends, and competitive analysis.

Limiting your data collection to one method or one type of customer will significantly reduce the effectiveness of your VOC strategy and activation.

Using VOC to Drive Process Improvements

VOC data can be used to analyze existing processes and formulate improvement strategies that directly address customer needs, thereby increasing customer retention, reducing support costs, and gaining new customers. A 2015 Aberdeen Group report concluded that companies using best-in-class VOC practices enjoyed ~10x the annual year-over-year revenue growth of those with less capable VOC programs.

Monitoring the impact of improvements on customer satisfaction over time

Monitoring and measuring the effect of process improvements on customer satisfaction ensures a continuous feedback loop between organizational efforts and customer expectations. Establish a sustainable feedback loop by:

Mitigating Misconceptions and Challenges

Knowing the challenges organizations often face when working with VOC data means you can use proven strategies to overcome them.

Misconceptions around VOC in Six Sigma

By debunking common misconceptions surrounding the implementation of VOC in Six Sigma, you can enable an accurate understanding of its value.

  • Collecting customer feedback is expensive. >> less so than losing customers.
  • Customers never give feedback. >> Is that because you aren’t asking them for it?
  • Customer feedback should only happen at the end. >> Preventing any changes that can save money from problems identified after the sale.

Common Obstacles Around Working with VOC Data

Common challenges in implementing VOC-driven Six Sigma initiatives include:

  • Accurately capturing the customer’s voice due to clear feedback channels.
  • Integrating VOC with existing processes without disrupting current operations.
  • Ensuring all stakeholders understand and value the importance of VOC data.
  • Prioritizing conflicting customer needs and expectations.

Tips to Mitigate Challenges and Ensuring Data Accuracy

To better ensure data-driven decisions, organizations should:

To better ensure data-driven decisions, organizations should:

  • Establish clear and multiple channels for customer feedback.
  • Train employees and stakeholders on the importance of VOC and Six Sigma methodologies.
  • Develop a structured approach to integrate VOC into processes using Six Sigma tools.
  • Use a prioritization matrix to manage and reconcile conflicting customer requirements.

Positive Impact of VOC on Customer Satisfaction and Business Performance

When the Project Charter, Scope, and Objectives are designed to incorporate VOC, customer needs and expectations are aligned to outcomes with benefits such as the ability to:

When the Project Charter, Scope, and Objectives are designed to incorporate VOC, customer needs and expectations are aligned to outcomes with benefits such as the ability to:

  • Consistently anticipate expectations (leading to sales gain) and mitigate disappointment (resulting in sales loss).
  • Foster a customer-centric workforce with engaged employees (reducing turnover).
  • Maintain a strong brand with loyal customers (adding to sales) when you consistently show that their voice matters.


Harnessing the Voice of the Customer in Six Sigma is not just a best practice; it’s a strategic imperative for organizations committed to delivering high-quality products or services. Organizations can elevate their process quality and efficiency by integrating VOC strategy into the DMAIC process. As leaders of Lean Six Sigma projects, Black Belts are pivotal in ensuring that the customer’s voice resonates throughout the improvement journey. Organizations can exceed customer expectations with a focus on Six Sigma integration and a commitment to meeting customer requirements.

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