A Critical to Quality Tree (also known as a CTQ Tree) is a Six Sigma tool used to identify the needs of the customer and translate that information into measurable product and process requirements. It allows organizations to understand the characteristics of a product or service that most drives quality for customers.

Before initiating any process improvement project, it’s important for a business to determine the characteristics of the product or service that are critical to quality as judged by customers – this is known as CTQ.

Creating a CTQ Tree determines the drivers behind those characteristics and helps companies find ways to meet them.

3 Components of a CTQ Tree

The first step to create a CTQ Tree involves listing the customer’s needs. Data in this area is typically attained through interaction with the customer. Six Sigma calls for breaking down these needs into three component areas.

Need –  What customer need are you fulfilling with your product or service?

Drivers – What elements or characteristics will your customers mostly likely consider when judging the quality of your product or service?

Requirements – What process or product requirements are needed to make those drivers meet customer standards?

Steps to Create a CTQ Tree

Now that you understand the three components of the CTQ Tree, there are certain steps to take to fill those areas with useful information. Most CTQ Trees are developed by project teams created explicitly for this task.

  • Determine the Need – It may be helpful to ask customers directly, or consult with customer service representatives or salespeople who frequently interact with customers
  • Determine at least three drivers – These are the elements that drive quality for customers who have the need you want to satisfy. Keep in mind that these are elements that must be present to satisfy customers.
  • Create the requirements – These are the standards that must be met to meet customers’ expectations for each driver.

Once requirements are developed, an organization can then take steps to make the changes or improvements needed.

Examples of CTQ Trees

Here are two examples of how a CTQ tree could work.

Cupcake Shop

Here’s an example of how you would breakdown the critical requirements for a cupcake shop (much of this applies to any kind of restaurant).

Need

Quality cupcakes and good service.

Drivers

1. Variety of products
2. Speed of service
3. Quality of ingredients

Requirements
For Variety of Toppings

  1. At least a dozen different cupcake toppings
    2. In addition to usual toppings, also include seasonal decoration options
    3. Identify non-cupcake products to offer, such as cocoa or coffee

For Speed of Service

  1. All customers waited on within a minute of entering shop
    2. All orders fulfilled within five minutes
    3. Deliver option offered for customers within certain miles of the shop

For Quality Ingredients

  1. All ingredients listed on menu
    2. Calories for each item listed
    3. All ingredients used are locally sourced where possible

Niche Website

Here’s another example, using the idea of starting a niche website for audiences interested in the local music scene.

Needs

Information on local music scene

Drivers

1. Timely information on local shows
2. In depth articles on the local music scene
3. Critical reviews

Requirements
For Timely Information on Local Shows

  1. A section of the site (perhaps the home page) dedicated to listing times and dates of shows well in advance
    2. A section that allows users to browse by local venue, with new shows added as they are scheduled
    3. Links to sites where customers can buy tickets

For In Depth Information on Local Music Scene

  1. Profiles of the biggest local bands
    2. Profiles of the biggest local venues
    3. Ongoing articles on festivals and concerts near your city

For Critical Reviews

  1. Reviews of music released by local bands
    2. Reviews of local shows
    3. Reviews of local venues, including food, drink, parking convenience, sound, etc.

Using a CTQ Tree allows you to break down a business into the most critical features that meet what your customers really want. For business owners and managers, it’s a critical addition to your Six Sigma toolbox.