Critical-to-quality tree
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A critical-to-quality (CTQ) tree is a tool that helps organizations identify which customer requirements are most important and how to achieve them. It is a hierarchical diagram with the customer requirements at the top and each subsequent level representing the required steps to measure, meet and exceed the customer requirement. Each level of the tree is broken down into measurable components that can be used to identify areas for improvement.
The CTQ tree is often used in Six Sigma projects to identify the customer needs that are the most important and to determine which areas are the most relevant to the organization’s processes. By understanding the customer's needs and what it takes to meet them, organizations can focus their efforts on areas that will have the greatest impact on customer satisfaction.
Components of CTQ
The CTQ tree is composed of four main components:
- Customer Requirements: The customer requirements are the desired outcomes that the customer is looking for. These are the starting point of the CTQ tree and should be clearly defined.
- Process Outputs: The process outputs are the measurable components that can be used to track and measure the customer requirements. These are the outputs of the process and should be clearly defined.
- Process Inputs: The process inputs are the components that go into the process and are used to produce the process outputs. These inputs should be clearly defined and monitored to ensure they are meeting the customer requirements.
- Process Controls: The process controls are the measures that are put in place to ensure that the process is running as intended and that the customer requirements are being met.
By mapping out the customer requirements and the process outputs, inputs and controls, the CTQ tree provides organizations with a clear picture of the areas that need to be improved in order to meet and exceed customer expectations. Through this tool, organizations can identify areas for improvement, develop strategies to address them and track progress over time.
Example of Critical-to-quality tree
A CTQ tree can be used to illustrate how customer requirements can be met through process inputs and outputs. For example, a company that produces computer monitors may use a CTQ tree to map out the customer requirements, process outputs, inputs and controls to ensure that the monitors are of the highest quality. The customer requirements might include a fast response time, clear images, and low power consumption. These requirements can then be broken down into measurable components such as response time, image clarity, and power consumption. The process outputs are the monitors that are produced, and the process inputs and controls are the components and measures that are used to produce the monitors. By mapping out the customer requirements, process outputs, inputs and controls, the company can identify areas for improvement and develop strategies to achieve the desired customer requirements.
When to use Critical-to-quality tree
Critical-to-quality trees can be used in a variety of situations, such as when an organization is looking to identify areas for improvement, when customer requirements are changing, when a product or service is being launched, or when customer feedback is being collected. The CTQ tree can help organizations focus their efforts on the areas that will have the greatest impact on customer satisfaction.
Types of Critical-to-quality tree
There are two main types of CTQ tree:
- The basic CTQ tree: This is the most common type of CTQ tree and is used to identify customer requirements and measure process outputs.
- The advanced CTQ tree: This type of CTQ tree is used to identify the process inputs and controls necessary to meet the customer requirements. It is more involved than the basic CTQ tree and requires more detailed analysis.
Advantages of Critical-to-quality tree
The CTQ tree has many advantages, including:
- It helps organizations identify the customer needs that are most important and how to best meet them.
- It provides a clear structure for identifying areas for improvement and developing strategies for addressing them.
- It allows organizations to track progress over time, so they can see how their efforts are paying off.
- It can be used to measure the performance of different processes and identify areas for improvement.
Limitations of Critical-to-quality tree
Although the CTQ tree is a useful tool for understanding customer requirements and mapping out the process, it does have some limitations.
- The CTQ tree is only as useful as the customer requirements that are identified. If the customer requirements are not well-defined, the process outputs, inputs and controls may not be accurate.
- The CTQ tree can be time-consuming to create and may not be the best tool for some organizations.
- The CTQ tree does not provide a comprehensive overview of the process, and may not identify areas for improvement that are not directly related to the customer requirements.
Other approaches related to the CTQ tree are Failure Mode and Effects Analysis (FMEA) and Design of Experiments (DOE).
- Failure Mode and Effects Analysis (FMEA): FMEA is a tool used to identify potential failure modes within a process, the associated effects of these failures and the actions taken to reduce their occurrence. It is used to identify and prioritize areas for improvement and ensure that potential problems are addressed before they occur.
- Design of Experiments (DOE): DOE is a tool used to identify the most effective process inputs to achieve a desired outcome. It is used to identify the optimal combination of inputs and to improve process performance.
The Critical-to-quality tree is a powerful tool that helps organizations identify customer needs, measure process performance and identify areas for improvement. By combining this tool with other approaches such as FMEA and DOE, organizations can ensure that their processes are running as intended and that customer requirements are being met.
Suggested literature
- He, Y., Tang, X., & Chang, W. (2010). Technical decomposition approach of critical to quality characteristics for product design for six sigma. Quality and Reliability Engineering International, 26(4), 325-339.
- Nazaruddin, N. (2022). Implementation of Quality Improvements to Minimize Critical to Quality Variations in Polyurethane Liquid Injection Processes. Journal of Applied Engineering and Technological Science (JAETS), 3(2), 139-148.
- Fleacă, B., & Corocăescu, M. (2019). CRITICAL TO QUALITY (CTQ) TREE TECHNIQUE TO IMPROVE TEACHING AND LEARNING PROCESS–THE CASE OF HIGHER EDUCATION. Proceedings of AC 2019 in Prague, 130.
