What is Critical to Quality in Six Sigma? CTQ Tree

  • Post last modified:29 March 2023
  • Reading time:11 mins read
  • Post category:Lean Six Sigma
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What is Critical to Quality in Six Sigma?

Critical to Quality (CTQ) is a term used in Six Sigma to describe the characteristics of a product, service or process that are most important to the customer. It is also known as the Voice of the Customer (VOC). The CTQs are identified through a variety of methods such as customer surveys, focus groups, feedback, and reviews.

The CTQs help organizations to focus their improvement efforts on the areas that matter most to the customer, which helps to improve customer satisfaction and loyalty. Once the CTQs have been identified, they are translated into measurable and quantifiable metrics that can be tracked and improved over time.

Deliverables: Critical to Quality Metrics

Commonly, deliverables are assumed to be the results of a project. However, this is not true because deliverables are just not limited to the actual results of a project; they also function as a tool to plan, manage and execute projects.

Deliverables are broadly divided into two types, namely project deliverables and process deliverables. Even though these two types have their specific purpose within the project, they need to be considered simultaneously and one type cannot be given more importance than the other.

Unlike day–to–day organizational operations, projects are initiated by the organization’s management to achieve specific and need-based outcomes. The purpose of the project and the need to undertake the project should be determined and expressed. This should be done no matter whether the project outcome is a product, a process, a plan, a policy, or any other outcome.

Once the outcome gets defined, it becomes deliverable. You read earlier that a deliverable is a tool for project planning, management, and execution. Many process deliverables may together produce the expected time and quality project deliverables. In short, a project deliverable is a final destination and the process deliverable can be considered as the roadmap to arrive at the final destination.

As mentioned earlier, the deliverables of the project should be identified at the beginning itself. These deliverables get further evolved and refined as the project progresses. A decision tree tool is used to execute the process of defining deliverables. For project and process deliverables, a series of questions are used to identify and define deliverables from the decision tree.

For the identification of project deliverables, the following considerations must take into account:

  • Identifying the form, nature, and function of the deliverable under consideration.

  • Determining the importance of the deliverable for the overall project.

  • What is the methodology to produce the deliverable? Does the organization have the required capabilities?

  • Have the cost and the feasibility of the cost been determined?

  • What are the timelines to complete or acquire deliverables?

  • Assessing the availability of alternatives and the pros and cons of all options.

For the identification of process deliverables, the following considerations are taken into account:

  • What kinds of deliverables are required for project completion?

  • What will be the deliverable completion timelines?

  • What deliverable formats need to be used?

  • What should be the responsibility matrix for planning, production, and implementation of deliverables?

  • What is the acceptance and approval matrix?

  • What will be the updating and maintenance methodology?

It is important to define deliverables because defined deliverables leave no room for predicting the actual results. While developing new products and services, it is important to incorporate quality as it leads to customer satisfaction and also helps the company to stand out from its competitors.

However, defining quality may be a challenge because sometimes the factors that may be important to customers may be easily overlooked. Thus, the Voice of the Customer (VOC) gets defined by a CTQ deliverable.

One of the important tools that can be used in defining CTQ deliverables is the Critical to Quality (CTQ) tree. This tree helps managers to establish the drivers of quality from the customer’s perspective. This tree helps in the decomposition of broader customer requirements into quantifiable elements.

Customer requirements usually include internal as well as external characteristics. Characteristics may include limits and factors that are related in any way to the product or service.

As an example, feedback from an organization’s customers that it needs to improve its customer service is too broad to be converted into action. In such cases, the project team can use the CTQ tree to break down a broad goal to identify specific, measurable requirements that the organization can use in performance improvement. CTQ trees were originally developed as part of Six Sigma but they are now used in many areas. A CTQ tree.

CTQ Tree

A CTQ tree can be used by adopting the following steps.

Step 1: Critical Need Identification

First and foremost, the CTQ tree is used to determine the critical needs of customers because the fulfillment of these needs would make the customer happy. For example, assume that a retail apparel store is being launched. A critical need for this store might be “should accept returns if required”.

The best option is to describe the needs in broad terms. In this way, missing out on important aspects of the next steps can be avoided. If there is a constraint in directly asking customers about their needs, managers can do brainstorming sessions with the team members who come in direct contact with customers such as sales and customer service teams.

Step 2: Determine the Quality Drivers

Once critical needs are determined, quality drivers need to be identified. Quality drivers are parameters that customers use to evaluate a product’s quality. For example, if the need is “should accept returns if required”, a quality driver may be “no deductions in the refund amount.”

This phase of quality driver determination should not be rushed through because it is important to determine quality drivers as comprehensively as possible. Yet again, the customer service and sales teams should be roped in if customers can’t be approached. Some special tools such as the Kano analysis and Philip Kotler’s Five product levels are found to be useful here.

The Kano model was developed by Professor Noriaki Kano in the 1980s. It is a theory of product development and customer satisfaction. According to the Kano model, customer preferences can be divided into five categories namely must-be quality, one-dimensional quality, attractive quality, indifferent quality, and reverse quality. Under the Kano model, these are the drivers of customer satisfaction.

Philip Kotler has also defined five product levels related to quality drivers. These five product levels include core product, generic product, expected product, augmented product, and potential product.

Step 3: Determine Measurable Performance Requirements

After identifying quality drivers, it’s time to identify measurable parameters of performance that need to be satisfied by each quality driver for giving a delightful experience to customers. In the absence of any measurable parameters, it may not be possible to evaluate the performance and quality of a product or service.

The ability of a business to deliver quality products is dependent on many variables such as the availability of enough resources or the required technology. An individual CTQ tree should be developed for each critical need. This would yield a comprehensive list of requirements that can be used to produce a product that gives customer delight.

In the earlier example of the retail apparel store, after identifying the Voice of the Customer (VOC), one critical need identified may include delightful customer service. Here, a CTQ tree can be created to prepare a list of measurable performance requirements.

Article Source
  • Ferraro, J. (2012). Project management for non-project managers. New York: AMACOM.

  • Jeff Furman. (2015). The Project Management Answer Book; 2nd Edition. Management Concepts, Inc.

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